Accessory device, imaging apparatus, and methods for controlling the same

ABSTRACT

A communication control unit of an interchangeable lens transmits information regarding distance information corresponding to the focus lens position to a camera main body to which the interchangeable lens unit is attached. The camera main body include a display unit, and perform display at the display unit based on the information received from the interchangeable lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/444,920, filed Jun. 18, 2019, which claims the benefit of JapanesePatent Application No. 2018-118125, filed Jun. 21, 2018, both of whichare hereby incorporated by reference herein in their entirety.

BACKGROUND Field of the Disclosure

The present disclosure relates to communication with an accessory deviceregarding information to be displayed at a display unit of an imagingapparatus.

Description of the Related Art

A technique is known in which a camera displays information regarding alens at a display unit such as a display included in the camera.

Japanese Patent Application Laid-Open No. 2010-2823 discusses atechnique for displaying focus position (object distance) informationregarding a lens at a display unit of a camera, instead of a displaymember of a lens barrel of the lens.

Further, Japanese Patent Application Laid-Open No. 2007-72407 discussesa technique for displaying position information regarding a focus lensof a lens at a camera and further displaying depth information at thecamera.

In the conventional art discussed in Japanese Patent ApplicationLaid-Open No. 2010-2823 and Japanese Patent Application Laid-Open No.2007-72407, the lens barrel of the lens does not need to include adisplay member. Thus, it is possible to obtain the effect ofcontributing to making the lens small and light. However, JapanesePatent Application Laid-Open No. 2010-2823 and Japanese PatentApplication Laid-Open No. 2007-72407 do not discuss the specific contentof data to be communicated from the lens to the camera to display focusdistance information and a scale at the display unit included in thecamera. Thus, Japanese Patent Application Laid-Open No. 2010-2823 andJapanese Patent Application Laid-Open No. 2007-72407 have an issue thatfor example, indices of distance information cannot be displayedaccording to the differences in specs between interchangeable lensessuch as a wide angle lens and a telephoto lens, or the differences inspecs between cameras, such as the numbers of pixels of display units ofthe cameras.

SUMMARY

The present disclosure is directed to providing an accessory device andan imaging apparatus capable of appropriately displaying informationaccording to an interchangeable lens at a camera display unit, andmethods for controlling the accessory device and the imaging apparatus.

According to embodiments of the present disclosure, an accessory devicethat is attachable to an imaging apparatus including a display unitincluding a display area where distance information corresponding to afocus lens position is displayed, and includes a focus lens that changesthe focus lens position includes a communication control unit configuredto control communication with the imaging apparatus via a communicationunit, wherein the communication control unit transmits (A) informationindicating the number of pieces of distance information displayed inassociation with the display area, (B) information indicating pieces ofdistance information the number of which is indicated by the number, (C)information indicating a position of each piece of distance informationrelative to the display area, and (D) information indicating distanceinformation corresponding to the focus lens position.

According to embodiments of the present disclosure, an imaging apparatusto which an accessory device including a focus lens that changes a focuslens position is attachable includes a display unit including a displayarea where distance information corresponding to the focus lens positionis displayed, and a communication control unit configured to controlcommunication with the accessory device via a communication unit,wherein the communication control unit receives (A) informationindicating the number of pieces of distance information displayed inassociation with the display area, (B) information indicating pieces ofdistance information the number of which is indicated by the number, (C)information indicating a position of each piece of distance informationrelative to the display area, and (D) information indicating distanceinformation corresponding to the focus lens position.

Further features of the present disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating a configuration of a camera systemincluding an imaging apparatus and an accessory device according to anexemplary embodiment of the present disclosure.

FIG. 1B is a diagram illustrating an example of an external appearanceof an interchangeable lens and various operation members.

FIG. 2 is a schematic diagram illustrating communication circuitsbetween the imaging apparatus and the accessory device.

FIGS. 3A and 3B are schematic diagrams illustrating communicationwaveforms in a communication mode M1.

FIG. 4 is a schematic diagram illustrating communication waveforms in acommunication mode M2.

FIGS. 5A, 5B, and 5C are schematic diagrams illustrating communicationwaveforms in a communication mode M3.

FIG. 6 is a flowchart illustrating a flow in which a communicationformat is determined in the accessory device and the imaging apparatus.

FIG. 7 is a flowchart illustrating a data communication flow in thecommunication mode M2.

FIG. 8 is a schematic screen diagram illustrating focus distance barinformation displayed in the imaging apparatus.

FIG. 9 is schematic screen diagrams illustrating magnificationinformation and depth-of-field information on the focus distance barinformation displayed in the imaging apparatus.

FIG. 10 is a flowchart illustrating a process regarding start operationsof the imaging apparatus and the accessory device.

FIG. 11A is a flowchart illustrating steady operations of the imagingapparatus and the accessory device.

FIG. 11B is a flowchart illustrating a process for updating display of acamera display unit.

FIG. 12 is a timing chart illustrating a communication status in steadystates of the imaging apparatus and the accessory device.

FIG. 13 is a diagram illustrating an example of display of a camerashake status according to a second exemplary embodiment.

FIG. 14 is a flowchart illustrating a process for displaying the camerashake status according to the second exemplary embodiment.

FIG. 15 is a flowchart illustrating a lens communication control unitprocess for displaying the camera shake status according to the secondexemplary embodiment.

FIG. 16 is diagrams illustrating examples of display of zoom positioninformation and various operation members of an interchangeable lensaccording to a third exemplary embodiment.

FIG. 17 is a flowchart illustrating a process for displaying the zoomposition information according to the third exemplary embodiment.

FIG. 18 is a flowchart illustrating a lens communication control unitprocess for displaying the zoom position information according to thethird exemplary embodiment.

FIGS. 19A and 19B are diagrams illustrating an issue.

DESCRIPTION OF THE EMBODIMENTS

A first exemplary embodiment is described. Based on the attacheddrawings, a detailed description will be given below of a communicationcontrol method for controlling communication between an interchangeablelens as an accessory device according to the present disclosure and acamera main body as an imaging apparatus according to the presentdisclosure. First, the definitions of terms in the present exemplaryembodiment are described.

A “communication format” refers to the rules of the entirety ofcommunication between the camera main body and the interchangeable lens.A “communication method” means a clock synchronization method and anasynchronous method. The clock synchronization method is a communicationmethod A, and the asynchronous method is a communication method B. A“data format” refers to whether a waiting-for-communication requestsignal (a busy signal) can be added. A data format that permits theaddition of the busy signal is a “format F1”, and a data format thatprohibits the addition of the busy signal is a “format F2”.

A “communication mode” means the combination of the communication methodand the data format. In the present exemplary embodiment, the followingthree communication modes are described. A “communication mode M1” isthe communication mode of the communication method A and the format F1.A “communication mode M2” is the communication mode of the communicationmethod B and the format F1. Further, a “communication mode M3” is thecommunication mode of the communication method B and the format F2.

The camera main body performs communication by appropriately switchingthe above communication modes M1, M2, and M3, and thereby can select anappropriate communication mode based on the combination of the cameramain body and the interchangeable lens or the image capturing mode.

For example, in a case where the camera main body and theinterchangeable lens are compatible with the communication mode M2, andtransmit and receive a large amount of data, the communication mode ofeach of the camera main body and the interchangeable lens is switched tothe communication mode M3, and then, high-speed data communication inwhich the addition of the busy signal is prohibited is executed. In acase where it takes some time to perform data processing in theinterchangeable lens, the communication mode of each of the camera mainbody and the interchangeable lens is switched to the communication modeM2, and then, data communication in which the addition of the busysignal is permitted is performed. This enables the execution of datacommunication in which communication does not break down between thecamera main body and the interchangeable lens.

<Basic Configurations of Camera Main Body 200 and Interchangeable Lens100>

FIG. 1A illustrates the configuration of an imaging system (hereinafterreferred to as a “camera system”) including a camera main body 200 as animaging apparatus according to the first exemplary embodiment of thepresent disclosure and an interchangeable lens 100 detachably attachedto the camera main body 200, as an accessory device according to thefirst exemplary embodiment of the present disclosure.

The camera main body 200 and the interchangeable lens 100 transmitcontrol commands and internal information via communication controlunits included in the camera main body 200 (a communication control unit209) and the interchangeable lens 100 (a communication control unit110). Each communication control unit supports a plurality ofcommunication formats. Based on the type of the communication data orthe purpose of communication, the communication control units switch tothe same communication format in synchronization with each other andthereby can select optimal communication formats for various situations.

First, the specific configurations of the interchangeable lens 100 andthe camera main body 200 are described. The interchangeable lens 100 andthe camera main body 200 are mechanically and electrically connectedtogether via mount portions that are joint mechanisms (not illustrated)and communication terminal groups included in the mount portions. Theinterchangeable lens 100 receives power supplied from the camera mainbody 200 via a power supply terminal (not illustrated) provided in themount portion of the interchangeable lens 100 and controls variousactuators and a lens microcomputer 111. Further, the interchangeablelens 100 and the camera main body 200 communicate with each other via acommunication terminal group 300 (illustrated in FIG. 2) provided in themount portions. The communication terminal group 300 includes acommunication terminal group 300 a (an example of a communication unitof the imaging apparatus) provided in the mount portion of the cameramain body 200, and a communication terminal group 300 b (an example of acommunication unit of the accessory device) provided in the mountportion of the interchangeable lens 100. The communication terminalgroup 300 a includes a communication terminal 301 a (an example of afirst communication unit of the imaging apparatus), a communicationterminal 302 a (an example of a second communication unit of the imagingapparatus), and a communication terminal 303 a (an example of a thirdcommunication unit of the imaging apparatus). The communication terminalgroup 300 b includes a communication terminal 301 b (an example of afirst communication unit of the accessory device), a communicationterminal 302 b (an example of a second communication unit of theaccessory device), and a communication terminal 303 b (an example of athird communication unit of the accessory device).

The interchangeable lens 100 includes an imaging optical system. Theimaging optical system includes a field lens 101, a variablemagnification lens 102 that changes the magnification, a diaphragm unit114 that adjusts the amount of light, an image blur correction lens 103,and a focus lens 104 that adjusts the focus, in this order from anobject OBJ side.

The variable magnification lens 102 and the focus lens 104 are held bylens holding frames 105 and 106, respectively. The lens holding frames105 and 106 are guided movably in the optical axis direction, which isindicated by a dashed line in FIG. 1A, by a guide shaft (notillustrated) and driven in the optical axis direction by stepping motors107 and 108, respectively. The stepping motors 107 and 108 move thevariable magnification lens 102 and the focus lens 104, respectively, insynchronization with driving pulses.

The image blur correction lens 103 moves in a direction orthogonal tothe optical axis of the imaging optical system, thereby reducing imageblur due to camera shake.

A lens microcomputer 111 is an accessory control unit that controls theoperations of components in the interchangeable lens 100. The lensmicrocomputer 111 receives a control command transmitted from the cameramain body 200 via the communication control unit 110 as an accessorycommunication control unit and receives a transmission request totransmit lens data. Further, the lens microcomputer 111 performs lenscontrol corresponding to the control command and transmits lens datacorresponding to the transmission request to the camera main body 200via the communication control unit 110.

Furthermore, in response to a command regarding a change in themagnification or focusing in the control command, the lens microcomputer111 outputs a driving signal to a zoom driving circuit 119 or a focusdriving circuit 120, thereby driving the stepping motor 107 or 108,respectively. Consequently, the lens microcomputer 111 performs a zoomprocess for controlling a magnification change operation by the variablemagnification lens 102, or an autofocus process for controlling a focusadjustment operation by the focus lens 104. A focus position detectionsensor 140 is a sensor for detecting the focus position when the focuslens 104 is caused to operate by the autofocus process or a manual focusprocess based on a user operation. The lens microcomputer 111 acquiresposition information regarding the focus lens 104 from the output of thefocus position detection sensor 140.

A lens barrel includes an autofocus/manual focus (AF/MF) selectionswitch described below with reference to FIG. 1B that is used to switchautofocus and manual focus, and a focus limit switch 141 that limits thedriving range of the focus lens 104. The focus limit switch 141 (alsoreferred to as a “first operation member”) is a switch that enables theselection of, for example, “0.8 m to ∞” and “3 m to ∞”. The focus limitswitch 141 performs control to move the focus lens 104 in a rangelimited by autofocus control. For example, to capture an image of ananimal in a cage, the range where the focus lens 104 is moved is limitedsuch that the closest side is not brought into focus. In an imagecapturing scene where focusing control should be performed by beinglimited to a predetermined distance range, a setting for thus limitingthe range is effective.

The diaphragm unit 114 includes diaphragm blades 114 a and 114 b. Thestates of the diaphragm blades 114 a and 114 b are detected by a Hallelement 115 and input to the lens microcomputer 111 via an amplificationcircuit 122 and an analog-to-digital (A/D) conversion circuit 123. Basedon an input signal from the A/D conversion circuit 123, the lensmicrocomputer 111 outputs a driving signal to a diaphragm drivingcircuit 121, thereby driving a diaphragm actuator 113. This controls theamount-of-light adjustment operation of the diaphragm unit 114.

Further, based on shake detected by a shake sensor (not illustrated) ofa vibrating gyroscope provided in the interchangeable lens 100, the lensmicrocomputer 111 drives an image stabilization actuator 126 via animage stabilization driving circuit 125. Consequently, an imagestabilization process for controlling the shifting operation of theimage blur correction lens 103 is performed. Furthermore, the shakesensor of the vibrating gyroscope outputs signal information as camerashake information regarding a user, and the lens microcomputer 111acquires the current camera shake state information.

In the present exemplary embodiment, for example, the focus positioninformation obtained by the focus position detection sensor 140, thecamera shake state information obtained by the shake sensor of thevibrating gyroscope, and zoom position information regarding a zoom lensare communicated to the camera main body 200. However, not only thefocus position, the camera shake state, and the zoom position, but alsoany information held in the interchangeable lens 100 may be acommunication target.

The camera main body 200 includes an image sensor 201 such as acharge-coupled device (CCD) sensor or a complementarymetal-oxide-semiconductor (CMOS) sensor, an A/D conversion circuit 202,a signal processing circuit 203, and a recording unit 204, a cameramicrocomputer 205, and a display unit 206 (an example of a displayunit).

The image sensor 201 photoelectrically converts an object image formedby the imaging optical system in the interchangeable lens 100 andoutputs an electric signal (an analog signal). The A/D conversioncircuit 202 converts the analog signal from the image sensor 201 into adigital signal. The signal processing circuit 203 performs various typesof image processing on the digital signal from the A/D conversioncircuit 202, thereby generating a video signal.

Further, the signal processing circuit 203 also generates informationregarding the contrast state of the object image, i.e., focusinformation indicating the focus state of the imaging optical system andluminance information indicating the exposure state of the imagingoptical system, from the video signal. The signal processing circuit 203outputs the video signal to the display unit 206, and the display unit206 displays the video signal as a live view image used to confirm thecomposition or the focus state.

In the live view image displayed at the display unit 206, various piecesof setting information, such as the shutter speed and the diaphragmsetting value, regarding the camera main body 200 are displayed.Further, in the present exemplary embodiment, the focus positioninformation regarding the lens 100 communicated from the lensmicrocomputer 111 via the communication control unit 110 is displayed ina superimposed manner on the live view screen. A specific example of thedisplay will be described below with reference to FIG. 8.

In response to inputs from camera operation members such as an imagecapturing instruction switch and various setting switches (notillustrated), the camera microcomputer 205 as a camera control unitcontrols the camera main body 200. Further, based on an operation on azoom switch (not illustrated), the camera microcomputer 205 transmits acontrol command regarding the magnification change operation of thevariable magnification lens 102 to the lens microcomputer 111 via acommunication interface (I/F) circuit 208. Furthermore, the cameramicrocomputer 205 transmits a control command regarding theamount-of-light adjustment operation of the diaphragm unit 114 based onthe luminance information or the focus adjustment operation of the focuslens 104 based on the focus information, to the lens microcomputer 111via the communication I/F circuit 208.

Further, In response to inputs from the camera operation members, a menuscreen for changing various settings of the camera can be displayed atthe display unit 206. It is possible to select whether to displayvarious pieces of information (such as object distance information)regarding the lens 100 according to the present exemplary embodiment atthe display unit 206, or select information as a target to be displayed(the focus position, magnification information, or camera shake state).

FIG. 1B illustrates an example of the external appearance of theinterchangeable lens 100 and various operation members. A ring 150 is azoom ring and can drive the zoom position from a wide area to atelephoto area based on a user operation or a communication instructionfrom the camera.

A ring 151 is a focus ring and enables the user to perform a manualfocus operation.

A switch 152 is an operation member that enables switching an autofocusmode and a manual focus mode.

A switch 153 is an operation member that enables switching whether toenable or disable an image stabilization function.

A switch 154 corresponds to the focus limit switch 141 in FIG. 1A. Inthis example, it is possible to switch among three states, i.e., “nolimit”, “0.8 m to ∞”, and “3.0 m to ∞”.

<Basic Configuration for Communication>

Next, with reference to FIG. 2, a description is given of communicationcircuits configured between the camera main body 200 and theinterchangeable lens 100, and communication control performed betweenthe camera main body 200 and the interchangeable lens 100. The cameramicrocomputer 205 has the function of managing a communication formatbetween the camera microcomputer 205 and the lens microcomputer 111, andthe function of notifying the lens microcomputer 111 of a transmissionrequest. The lens microcomputer 111 has the function of generating lensdata, and the function of transmitting the lens data.

The camera microcomputer 205 and the lens microcomputer 111 communicatewith each other via the communication terminal group 300 provided in themount portions, and the communication I/F circuits 208 and acommunication I/F circuit 112 provided in the camera microcomputer 205and the lens microcomputer 111, respectively.

In the present exemplary embodiment, the camera microcomputer 205 andthe lens microcomputer 111 perform serial communication by thecommunication methods A and B, which are three-wire communicationmethods using three channels, i.e., first, second, and thirdcommunication channels.

Through the first communication channel, communication is performed viathe communication terminals 301 a and 301 b.

The first communication channel is a notification channel that serves asa clock channel in the communication method A and serves as atransmission request channel in the communication method B.

Through the second communication channel, communication is performed viathe communication terminals 302 a and 302 b.

The second communication channel is used to transmit camera data fromthe camera microcomputer 205 to the lens microcomputer 111. The cameradata transmitted as a signal from the camera microcomputer 205 to thelens microcomputer 111 through the second communication channel isreferred to as a “camera data signal DCL”.

Through the third communication channel, communication is performed viathe communication terminals 303 a and 303 b. The third communicationchannel is used to transmit lens data from the lens microcomputer 111 tothe camera microcomputer 205. The lens data transmitted as a signal fromthe lens microcomputer 111 to the camera microcomputer 205 through thethird communication channel is referred to as a “lens data signal DLC”.

<Communication Method A>

First, communication by the communication method A is described. In thecommunication method A, the camera microcomputer 205 as a communicationmaster outputs a clock signal LCLK to the lens microcomputer 111 as acommunication slave via the clock channel. The camera data signal DCLincludes a control command or a transmission request command from thecamera microcomputer 205 to the lens microcomputer 111. On the otherhand, the lens data signal DLC includes various pieces of data to betransmitted from the lens microcomputer 111 to the camera microcomputer205 in synchronization with the clock signal LCLK. The cameramicrocomputer 205 and the lens microcomputer 111 can communicate witheach other by a full-duplex communication method (a full-duplex method)for simultaneously transmitting and receiving data to and from eachother in synchronization with the common clock signal LCLK.

FIGS. 3A and 3B illustrate the waveforms of signals exchanged betweenthe camera microcomputer 205 and the lens microcomputer 111. The rulesof the procedure of the exchange are referred to as a “communicationprotocol”.

FIG. 3A illustrates signal waveforms of one frame, which is the smallestunit of communication. First, the camera microcomputer 205 outputs theclock signal LCLK including a set of eight-cycle clock pulses and alsotransmits the camera data signal DCL to the lens microcomputer 111 insynchronization with the clock signal LCLK. Simultaneously with this,the camera microcomputer 205 receives the lens data signal DLC outputfrom the lens microcomputer 111 in synchronization with the clock signalLCLK.

One byte (eight bits) of data is thus transmitted and received betweenthe lens microcomputer 111 and the camera microcomputer 205 insynchronization with the clock signal LCLK as a set. The period of thetransmission and reception of the one byte of data is referred to as a“data frame”. After the transmission and reception of the one byte ofdata, the lens microcomputer 111 transmits a signal (hereinafterreferred to as a “busy signal”) for notifying the camera microcomputer205 of a waiting-for-communication request BUSY, thereby inserting awaiting-for-communication period. The waiting-for-communication periodis referred to as a “busy frame”. While receiving the busy frame, thecamera microcomputer 205 is in a waiting-for-communication state. Then,the unit of communication composed of a set of the data frame period andthe busy frame period is one frame. There is also a case where the busyframe is not added depending on the communication status. In this case,however, one frame is composed only of the data frame period.

FIG. 3B illustrates signal waveforms when the camera microcomputer 205transmits a request command CMD1 to the lens microcomputer 111 andreceives two bytes of lens data DT1 (DT1 a and DT1 b) corresponding tothe request command CMD1 from the lens microcomputer 111. FIG. 3Billustrates an example where data communication is executed according to“communication CMD1”.

Between the camera microcomputer 205 and the lens microcomputer 111, thetypes and the numbers of bytes of lens data DT corresponding to aplurality of types of commands CMD are determined in advance. If thecamera microcomputer 205 as a communication master transmits aparticular command CMD to the lens microcomputer 111, then based oninformation regarding the number of bytes of lens data corresponding tothe command CMD, the lens microcomputer 111 transmits a required clockfrequency to the camera microcomputer 205. Further, the processing ofthe lens microcomputer 111 on the command CMD1 includes the process ofsuperimposing the busy signal on the clock signal LCLK of each frame,and the above busy frames are inserted between data frames.

In the communication CMD1, the camera microcomputer 205 transmits theclock signal LCLK to the lens microcomputer 111 and transmits therequest command CMD1 requesting the transmission of the lens data DT1,as the camera data signal DCL to the lens microcomputer 111. The lensdata signal DLC of this frame is treated as invalid data.

Next, the camera microcomputer 205 outputs the clock signal LCLK ineight cycles through the clock channel and then switches the clockchannel on the camera microcomputer 205 side (the camera main body 200side) from an output setting to an input setting. If the switching ofthe clock channel on the camera microcomputer 205 side is completed, thelens microcomputer 111 switches the clock channel on the lensmicrocomputer 111 side (the interchangeable lens 100 side) from an inputsetting to an output setting. Then, to notify the camera microcomputer205 of the waiting-for-communication request BUSY, the lensmicrocomputer 111 sets the voltage level of the clock channel to low.Consequently, the lens microcomputer 111 superimposes the busy signal onthe clock channel. In the period when the camera microcomputer 205 isnotified of the waiting-for-communication request BUSY, the cameramicrocomputer 205 maintains the input setting of the clock channel andstops communicating with the lens microcomputer 111.

In the period when the lens microcomputer 111 notifies the cameramicrocomputer 205 of the waiting-for-communication request BUSY, thelens microcomputer 111 generates the lens data DT1 corresponding to thetransmission request command CMD1. Then, if preparation for transmittingthe lens data DT1 as the lens data signal DLC of the next frame iscompleted, the lens microcomputer 111 switches the signal level of theclock channel on the lens microcomputer 111 side to high and cancels thewaiting-for-communication request BUSY.

If recognizing the cancellation of the waiting-for-communication requestBUSY, the camera microcomputer 205 transmits the clock signal LCLK ofone frame to the lens microcomputer 111, thereby receiving the lens dataDT1 a from the lens microcomputer 111. In the next frame, the cameramicrocomputer 205 outputs the clock signal LCLK in eight cycles again,and the camera microcomputer 205 and the lens microcomputer 111 repeatoperations similar to the above, whereby the camera microcomputer 205receives the lens data DT1 b from the lens microcomputer 111.

<Communication Method B>

Next, communication by the communication method B is described. At thesame time, the communication mode M2 for performing communication in theformat F1 using the communication method B is also described. FIG. 4illustrates the waveforms of communication signals exchanged between thecamera microcomputer 205 and the lens microcomputer 111 in thecommunication mode M2. As described above, in the format F1, a busyframe is selectively added to the lens data signal DLC.

In the communication method B, the transmission request channel is usedfor the camera microcomputer 205 as a communication master to notify thelens microcomputer 111 as a communication slave of a transmissionrequest to transmit lens data. The notification through the transmissionrequest channel is given by switching the level (the voltage level) of asignal through the transmission request channel between high (a firstlevel) and low (a second level). In the following description, thesignal supplied to the transmission request channel in the communicationmethod B is referred to as a “transmission request signal RTS”.

Similar to the communication method A, a first data communicationchannel (corresponding to the third communication channel) is used totransmit the lens data signal DLC including various pieces of data fromthe lens microcomputer 111 to the camera microcomputer 205. Similar tothe communication method A, a second data communication channel(corresponding to the second communication channel) is also used totransmit the camera data signal DCL including a control command or atransmission request command from the camera microcomputer 205 to thelens microcomputer 111.

In the communication method B, unlike the communication method A, thecamera microcomputer 205 and the lens microcomputer 111 do not transmitand receive data in synchronization with a common clock signal, but seta communication speed in advance and transmit and receive data to andfrom each other at a communication bit rate based on the setting. Thecommunication bit rate indicates the amount of data that can betransferred in one second, and the unit of the communication bit rate isrepresented by bits per second (bps).

In the present exemplary embodiment, also in the communication method B,similar to the communication method A, the camera microcomputer 205 andthe lens microcomputer 111 communicate with each other by a full-duplexcommunication method (a full-duplex method) for transmitting andreceiving data to and from each other.

FIG. 4 illustrates signal waveforms of one frame, which is the smallestunit of communication. The camera data signal DCL and the lens datasignal DLC are partially different in the breakdown of the data formatof one frame.

First, the data format of the lens data signal DLC is described. Thelens data signal DLC of one frame is composed of a data frame in thefirst half of the lens data signal DLC and a busy frame following thedata frame. In the state where data is not transmitted, the signal levelof the lens data signal DLC is kept high.

To notify the camera microcomputer 205 of the start of the transmissionof one frame of the lens data signal DLC, the lens microcomputer 111sets the voltage level of the lens data signal DLC to low in one bitperiod. The one bit period is referred to as a “start bit ST”, and thedata frame starts from the start bit ST. Next, the lens microcomputer111 transmits one byte of lens data in an eight-bit period from thesecond bit following the start bit ST to the ninth bit.

The bit array of the data starts with the most significant data D7,continues with data D6 and D5, and ends with the least significant dataDO in a most significant bit (MSB) first format. Then, the lensmicrocomputer 111 adds one bit of parity information (PA) to the tenthbit and sets the voltage level of the lens data signal DLC to high inthe period of a stop bit SP indicating the end of the one frame.Consequently, the data frame period starting from the start bit ST ends.The parity information may not need to be one bit. Alternatively, aplurality of bits of parity information may be added. Further, theparity information is not essential. Alternatively, a format may beemployed in which the parity information is not added.

Next, as illustrated in “DLC (BUSY: present)” in FIG. 4, the lensmicrocomputer 111 adds the busy frame after the stop bit SP. Similar tothe communication method A, the busy frame indicates the period of thewaiting-for-communication request BUSY of which the lens microcomputer111 notifies the camera microcomputer 205. The lens microcomputer 111keeps the signal level of the lens data signal DLC low until thewaiting-for-communication request BUSY is canceled.

On the other hand, there is a case where the lens microcomputer 111 doesnot need to notify the camera microcomputer 205 of thewaiting-for-communication request BUSY. For this case, as illustrated in“DLC (BUSY: absent)” in FIG. 4, a data format in which one frame iscomposed without adding the busy frame (hereinafter also referred to asa “busy notification”) is also provided. That is, as the data format ofthe lens data signal DLC, the lens data signal DLC to which the busynotification is added, and the lens data signal DLC to which the busynotification is not added can be selected based on the processing statuson the lens microcomputer 111 side.

A description is given of an identification method for identifying thepresence or absence of the busy notification by the camera microcomputer205. A signal waveform illustrated in “DLC (BUSY: absent)” in FIG. 4 anda signal waveform illustrated in “DLC (BUSY: present)” in FIG. 4 includebit positions B1 and B2. The camera microcomputer 205 selects either ofthe bit positions B1 and B2 as a busy identification position P foridentifying the presence or absence of the busy notification. Asdescribed above, in the present exemplary embodiment, a data format isemployed in which the busy identification position P is selected fromthe bit positions B1 and B2. Consequently, it is possible to address theissue that the processing time until the busy notification (the lensdata signal DLC is low) is finalized after the transmission of the dataframe of the lens data signal DLC varies depending on the processingperformance of the lens microcomputer 111.

Which of the bit positions B1 and B2 is to be selected as the busyidentification position P is determined through communication betweenthe camera microcomputer 205 and the lens microcomputer 111 before thecommunication by the communication method B is performed. The busyidentification position P may not need to be fixed to either of the bitpositions B1 and B2, and may be changed depending on the processingcapabilities of the camera microcomputer 205 and the lens microcomputer111. The busy identification position P is not limited to the bitpositions B1 and B2, and can be set to a predetermined position afterthe stop bit SP.

A description is given of the reason for employing a data format inwhich the busy frame added to the clock signal LCLK in the communicationmethod A is added to the lens data signal DLC in the communicationmethod B.

In the communication method A, the clock signal LCLK output from thecamera microcomputer 205 as the communication master and the busy signaloutput from the lens microcomputer 111 as the communication slave needto be exchanged through the same clock channel. Thus, collision betweenthe outputs of the camera microcomputer 205 and the lens microcomputer111 is prevented by a time division method. That is, collision betweenthe outputs can be prevented by appropriately assigning the periods whenthe camera microcomputer 205 and the lens microcomputer 111 are allowedto provide outputs through the clock channel.

In the time division method, however, collision between the outputs ofthe camera microcomputer 205 and the lens microcomputer 111 needs to becertainly prevented. Thus, between the time when the cameramicrocomputer 205 completes the output of the clock signal LCLKincluding eight pulses and the time when the lens microcomputer 111 ispermitted to output the busy signal, a certain output prohibition periodwhen both the microcomputers 205 and 111 are prohibited from providingoutputs is inserted. The output prohibition period is a communicationdisabled period when the camera microcomputer 205 and the lensmicrocomputer 111 cannot communicate with each other. This reduces theeffective communication speed.

To resolve such an issue, in the communication method B, a data formatis employed in which the busy frame from the lens microcomputer 111 isadded to the lens data signal DLC in the first data communicationchannel, which is a dedicated output channel for the lens microcomputer111.

Next, the data format of the camera data signal DCL is described. Thespecifications of a data frame of one frame of the camera data signalDCL are similar to those of the lens data signal DLC. However, unlikethe lens data signal DLC, the addition of a busy frame to the cameradata signal DCL is prohibited.

Next, the procedure of communication between the camera microcomputer205 and the lens microcomputer 111 in the communication method B isdescribed. First, if an event for starting communication with the lensmicrocomputer 111 occurs, the camera microcomputer 205 sets the voltagelevel of the transmission request signal RTS to low (hereinafter,“asserts the transmission request signal RTS”), thereby notifying thelens microcomputer 111 of a communication request.

If detecting the communication request due to the fact that the voltagelevel of the transmission request signal RTS changes to low, the lensmicrocomputer 111 performs a process for generating the lens data signalDLC to be transmitted to the camera microcomputer 205. Then, ifpreparation for the transmission of the lens data signal DLC iscompleted, the lens microcomputer 111 starts transmitting the lens datasignal DLC of one frame via the first data communication channel. Atthis time, within a setting time set between the camera microcomputer205 and the lens microcomputer 111 from the time when the voltage levelof the communication request signal RTS changes to low, the lensmicrocomputer 111 starts transmitting the lens data signal DLC.

That is, in the communication method B, lens data to be transmitted mayonly need to be finalized between the time when the voltage level of thecommunication request signal RTS changes to low and the time when thetransmission of the lens data signal DLC is started. Unlike thecommunication method A, there is no strict restriction such as needingto finalize lens data to be transmitted by the time when the first clockpulse is input. Thus, it is possible to flexibly set the timing when thetransmission of the lens data signal DLC is started.

Next, according to the detection of a start bit ST added to thebeginning of a data frame of the lens data signal DLC received from thelens microcomputer 111, the camera microcomputer 205 changes the voltagelevel of the transmission request signal RTS back to high (hereinafter,“negates the transmission request signal RTS”). Consequently, the cameramicrocomputer 205 cancels the transmission request and also startstransmitting the camera data signal DCL through the second communicationchannel. It does not matter which of the negation of the transmissionrequest signal RTS and the start of the transmission of the camera datasignal DCL is performed first. These processes may only need to beperformed by the time when the reception of the data frame of the lensdata signal DLC is completed.

If the lens microcomputer 111 having transmitted the data frame of thelens data signal DLC needs to notify the camera microcomputer 205 of thewaiting-for-communication request BUSY, the lens microcomputer 111 addsa busy frame to the lens data signal DLC. The camera microcomputer 205monitors the presence or absence of the notification of thewaiting-for-communication request BUSY. While the camera microcomputer205 is notified of the waiting-for-communication request BUSY, thecamera microcomputer 205 is prohibited from asserting the transmissionrequest signal RTS for the next transmission request.

The lens microcomputer 111 executes necessary processing in the periodwhen the lens microcomputer 111 keeps the camera microcomputer 205waiting for communication, using the waiting-for-communication requestBUSY. After preparation for the next communication is completed, thelens microcomputer 111 cancels the waiting-for-communication requestBUSY. Under the condition that the waiting-for-communication requestBUSY is canceled and the transmission of the data frame of the cameradata signal DCL is completed, the camera microcomputer 205 is permittedto assert the transmission request signal RTS for the next transmissionrequest.

As described above, in the present exemplary embodiment, according tothe fact that the transmission request signal RTS is asserted using acommunication start event in the camera microcomputer 205 as a trigger,the lens microcomputer 111 starts transmitting the data frame of thelens data signal DLC to the camera microcomputer 205. Then, according tothe detection of the start bit ST of the lens data signal DLC, thecamera microcomputer 205 starts transmitting the data frame of thecamera data signal DCL to the lens microcomputer 111.

At this time, the lens microcomputer 111 adds a busy frame after thedata frame of the lens data signal DLC for the waiting-for-communicationrequest BUSY, where necessary. Then, the lens microcomputer 111 cancelsthe waiting-for-communication request BUSY, whereby a communicationprocess for communicating one frame is completed. By the communicationprocess, the camera microcomputer 205 and the lens microcomputer 111transmit and receive one byte of communication data to and from eachother.

Next, the communication mode M3 for performing communication in theformat F2 using the communication method B is described. FIG. 5Aillustrates the waveforms of communication signals exchanged between thecamera microcomputer 205 and the lens microcomputer 111 in thecommunication mode M3. FIG. 5A illustrates the waveforms ofcommunication signals when data of three frames is continuouslytransmitted. As described above, in the format F2, the addition of thewaiting-for-communication request BUSY to the lens data signal DLC isprohibited.

In the data format of the lens data signal DLC in the communication modeM3, one frame is composed only of a data frame, and a busy frame is notpresent. Thus, in the communication mode M3, the lens microcomputer 111cannot notify the camera microcomputer 205 of thewaiting-for-communication request BUSY.

Such a format F2 is used to perform continuous communication in whichthe intervals between frames are shortened when a relatively largeamount of data is transferred between the camera microcomputer 205 andthe lens microcomputer 111. That is, the format F2 enables high-speedcommunication of a large amount of data.

Next, a description will be given of a communication control processbetween the camera microcomputer 205 and the lens microcomputer 111,which is the feature of the present exemplary embodiment. FIG. 5Billustrates the waveforms of communication signals when the cameramicrocomputer 205 and the lens microcomputer 111 continuously transmitand receive the camera data signal DCL and the lens data signal DLC of nframes. If an event for starting communication with the lensmicrocomputer 111 occurs, the camera microcomputer 205 asserts thetransmission request signal RTS. In the format F2, unlike the format F1,the camera microcomputer 205 does not need to negate the transmissionrequest signal RTS with respect to each frame. Thus, during the statewhere data can be continuously transmitted and received, the cameramicrocomputer 205 maintains the asserted state of the transmissionrequest signal RTS.

If detecting a communication request due to the assertion of thetransmission request signal RTS, the lens microcomputer 111 performs aprocess for generating the lens data signal DLC to be transmitted to thecamera microcomputer 205. Then, if preparation for the transmission ofthe lens data signal DLC is completed, the lens microcomputer 111 startstransmitting the lens data signal DLC (DL1) of the first frame throughthe first data communication channel.

The lens microcomputer 111 having transmitted a data frame of the lensdata signal DLC of the first frame confirms the transmission requestsignal RTS again. At this time, if the transmission request signal RTSis in the asserted state, the lens microcomputer 111 transmits the lensdata signal DLC (DL2) of the next second frame to the cameramicrocomputer 205, following the first frame of which the transmissionis completed. While the asserted state of the transmission requestsignal RTS is thus maintained, the lens data signal DLC (DL1 to DLn)from the lens microcomputer 111 is continuously transmitted to thecamera microcomputer 205. Then, if the transmission of the lens datasignal DLC of the n frames determined in advance is completed, thetransmission of the lens data signal DLC is stopped.

According to the detection of a start bit ST of each frame of the lensdata signal DLC from the lens microcomputer 111, the cameramicrocomputer 205 starts transmitting the camera data signal DCL (DC1 toDCn) of the n frames through the second communication channel.

FIG. 5C illustrates the waveforms of communication signals in a casewhere the camera microcomputer 205 or the lens microcomputer 111 givesan instruction to temporarily wait for communication during thecommunication of the continuous transmission and reception of dataillustrated in FIG. 5B. Also in this case, the camera microcomputer 205asserts the communication request signal RTS, whereby the lensmicrocomputer 111 starts transmitting the lens data signal DLC. Then,according to the detection of a start bit ST of the lens data signalDLC, the camera microcomputer 205 starts transmitting the camera datasignal DCL.

A waiting-for-communication period T2 w 1 indicates the period when thecamera microcomputer 205 gives an instruction to wait for communication.The camera microcomputer 205 temporarily negates the transmissionrequest signal RTS, thereby notifying the lens microcomputer 111 of thisinstruction. If detecting the negation of the transmission requestsignal RTS, the lens microcomputer 111 completes the transmission of aframe (DL6 in FIG. 5C: hereinafter referred to as a “suspension frame”)of the lens data signal DLC that is being transmitted when the negationis detected. Then, the lens microcomputer 111 suspends the transmission.

In response to the suspension of the transmission of the lens datasignal DLC, the camera microcomputer 205 also transmits a frame (DC6)corresponding to the suspension frame in the camera data signal DCL andthen suspends the transmission of the camera data signal DCL. By suchcommunication control, even in a case where a waiting-for-communicationinstruction is given during the communication of the continuoustransmission and reception of data, it is possible to manage the lensdata signal DLC and the camera data signal DCL so that the numbers oftransmitted frames of the lens data signal DLC and the camera datasignal DCL are the same.

If a waiting-for-communication request event is not present, the cameramicrocomputer 205 asserts the transmission request signal RTS again andthereby can instruct the lens microcomputer 111 to resume thecommunication. In response to the communication resumption instruction,the lens microcomputer 111 resumes the transmission of the lens datasignal DLC from a frame (DL7: hereinafter referred to as a “resumptionframe”) following the suspension frame. Then, according to the detectionof a start bit ST of the resumption frame, the camera microcomputer 205resumes the transmission of a frame (DC7) corresponding to theresumption frame in the camera data signal DCL.

On the other hand, a waiting-for-communication period T2 w 2 indicatesthe period when the lens microcomputer 111 gives an instruction to waitfor communication. In FIG. 5C, after the waiting-for-communicationperiod T2 w 1 ends, neither the camera microcomputer 205 nor the lensmicrocomputer 111 gives an instruction to wait for communication, andthe camera microcomputer 205 and the lens microcomputer 111 continuouslytransmit and receive data to and from each other in the order of theresumption frames DL7 and DC7, frames DL8 and DC8 following theresumption frames DL7 and DC7, and frames DL9 and DC9.

Then, when the transmission of the frame DL9 from the lens microcomputer111 (the reception of the frame DC9 from the camera microcomputer 205)is completed, a waiting-for-communication request event occurs, wherebythe lens microcomputer 111 notifies the camera microcomputer 205 of awaiting-for-communication instruction.

When the transmission request signal RTS is in an asserted state, thelens microcomputer 111 does not transmit the lens data signal DLC,thereby notifying the camera microcomputer 205 that the communication isto be suspended.

The camera microcomputer 205 constantly monitors a start bit ST of eachframe of the lens data signal DLC. A rule is made that if the cameramicrocomputer 205 does not detect the start bit ST, the cameramicrocomputer 205 suspends the transmission of the next frame of thecamera data signal DCL. Even if the transmission request signal RTS isasserted, but if the camera microcomputer 205 does not receive the lensdata signal DLC (DL10 in FIG. 5C) from the lens microcomputer 111, thecamera microcomputer 205 suspends the communication without transmittingthe camera data signal DCL (DC10). The camera microcomputer 205 keepsthe transmission request signal RTS in the asserted state during thewaiting-for-communication period T2 w 2 when the lens microcomputer 111gives an instruction.

Then, a waiting-for-communication request event is not present in thelens microcomputer 111, and the lens microcomputer 111 resumes thetransmission of the resumption frame DL10 in the lens data signal DLC.According to the detection of the start bit ST of the resumption frameDL10, the camera microcomputer 205 resumes the transmission of thecorresponding frame DC10 in the camera data signal DCL.

Next, with reference to FIG. 6, a description will be given of aprocedure for determining a communication format between the cameramicrocomputer 205 and the lens microcomputer 111. based on acommunication control program, which is a computer program, the cameramicrocomputer 205 and the lens microcomputer 111 perform communicationcontrol illustrated in flowcharts in FIGS. 6 and 7.

First, if the interchangeable lens 100 is attached to the camera mainbody 200, then in steps S100 and S200, the camera microcomputer 205 andthe lens microcomputer 111 set as a communication format an initialcommunication format in which the establishment of communication isguaranteed. At this time, the initial communication format may be thecombination of a communication method and a data format discussed in thepresent exemplary embodiment, or may be a communication format otherthan the combination of a communication method and a data formatdiscussed in the present exemplary embodiment. When an asynchronouscommunication format is selected as the initial communication format, itis desirable to set the busy identification position P such thatcommunication can be executed no matter what camera and interchangeablelens are combined together.

Next, in step S101, the camera microcomputer 205 transmits, to the lensmicrocomputer 111, camera identification information indicating acommunication format with which the camera main body 200 is compatible.Further, in step S202, the lens microcomputer 111 transmits, to thecamera microcomputer 205, lens identification information indicating acommunication format with which the interchangeable lens 100 iscompatible.

At this time, the “identification information” includes informationindicating with which of the clock synchronization communication methodand the asynchronous communication method the camera main body 200 andthe interchangeable lens 100 are compatible, and information indicatingthe range of a communication bit rate with which the camera main body200 and the interchangeable lens 100 each are compatible. Theidentification information also includes information indicating the busyidentification position P.

In step S102, the camera microcomputer 205 receives the lensidentification information. In step S201, the lens microcomputer 111receives the camera identification information. In the flowchart in FIG.6, after the camera identification information is transmitted, the lensidentification information is transmitted. Alternatively, thetransmission of the camera identification information and thetransmission of the lens identification information may besimultaneously performed. Yet alternatively, after the lensidentification information is transmitted, the camera identificationinformation may be transmitted.

Next, in steps S103 and S203, a communication format for the subsequentcommunication is set. Specifically, the camera microcomputer 205 and thelens microcomputer 111 determine as a communication bit rate the fastestrate among communication bit rates with which the camera microcomputer205 and the lens microcomputer 111 are compatible. Further, the cameramicrocomputer 205 and the lens microcomputer 111 set as the busyidentification position P the closest position to a stop bit SP amongbusy identification positions P with which the camera microcomputer 205and the lens microcomputer 111 are compatible.

Through the above communication control, the communication mode of thecamera microcomputer 205 and the lens microcomputer 111 shifts to thestate of the communication mode M2.

<Data Communication Flow in Asynchronous Communication Method>

Next, with reference to FIG. 7, a data communication flow in theasynchronous communication method will be described. With reference toFIG. 7, a description is given of a communication flow in a data formatin which the addition of the busy signal is permitted.

The camera microcomputer 205 monitors whether a communication event forstarting communication with the lens microcomputer 111 occurs. If acommunication event occurs in step S110 (Yes in step S110), theprocessing proceeds to step S111. In step S111, as described above, thecamera microcomputer 205 asserts the communication request signal RTS,thereby making a communication request to the lens microcomputer 111.

The lens microcomputer 111 monitors whether the communication requestsignal RTS is asserted. If the lens microcomputer 111 recognizes in stepS210 that the communication request signal RTS is asserted (Yes in stepS210), the processing proceeds to step S211. In step S211, the lensmicrocomputer 111 transmits the lens data signal DLC to the cameramicrocomputer 205 via the first data communication channel.

If the camera microcomputer 205 receives the lens data signal DLC fromthe lens microcomputer 111 (YES in step S112), the processing proceedsto step S113. In step S113, the camera microcomputer 205 negates thecommunication request signal RTS. Then, the processing proceeds to stepS114. In step S114, the camera microcomputer 205 transmits the cameradata signal DCL to the lens microcomputer 111 via the second datacommunication channel.

If the lens microcomputer 111 detects the start of the reception of thecamera data signal DCL in step S212 (Yes in step S212), the processingproceeds to step S213. In step S213, the lens microcomputer 111 performsa process for receiving the camera data signal DCL. In step S214, inparallel with the process of step S213, the lens microcomputer 111determines whether the lens microcomputer 111 needs to notify the cameramicrocomputer 205 of the waiting-for-communication request BUSY. If thelens microcomputer 111 does not need to notify the camera microcomputer205 of the waiting-for-communication request BUSY (No in step S214), theprocessing proceeds to step S218. In step S218, the lens microcomputer111 waits until the reception of the camera data signal DCL iscompleted.

If, on the other hand, the lens microcomputer 111 needs to notify thecamera microcomputer 205 of the waiting-for-communication request BUSY(Yes in step S214), the processing proceeds to step S215. In step S215,the lens microcomputer 111 adds a busy frame to the lens data signalDLC. While notifying the camera microcomputer 205 of thewaiting-for-communication request BUSY, the lens microcomputer 111executes necessary processing. After preparation for the nextcommunication is completed (Yes in step S216), then in step S217, thelens microcomputer 111 cancels the waiting-for-communication requestBUSY. After the lens microcomputer 111 cancels thewaiting-for-communication request BUSY, the processing proceeds to stepS218. In step S218, the lens microcomputer 111 waits until the receptionof the camera data signal DCL is completed. If the reception of thecamera data signal DCL is completed (Yes in step S218), the processingreturns to step S210. In step S210, the lens microcomputer 111 continuesto monitor whether the communication request signal RTS is asserted.

If receiving the notification of the waiting-for-communication requestBUSY in step S115 (Yes in step S115), the camera microcomputer 205 waitsuntil the waiting-for-communication request BUSY is canceled. If thewaiting-for-communication request BUSY is canceled (YES in step S116),the processing proceeds to step S117. In step S117, the cameramicrocomputer 205 determines whether the transmission of the camera datasignal DCL is completed. Further, also if the notification of thewaiting-for-communication request BUSY is not received in step S115 (Noin step S115), the processing proceeds to step S117. In step S117, thecamera microcomputer 205 determines whether the transmission of thecamera data signal DCL is completed. If it is determined in step S117that the transmission of the camera data signal DCL is completed (Yes instep S117), the processing returns to step S110. In step S110, thecamera microcomputer 205 continues to monitor whether a communicationevent occurs.

As described above, the present exemplary embodiment relates tocommunication control in asynchronous communication (the communicationmethod B) composed of three channels. Via the first data communicationchannel, which is a dedicated output channel for the lens microcomputer111, the lens microcomputer 111 transmits the waiting-for-communicationrequest BUSY to the camera microcomputer 205. On the other hand, thetransmission request signal RTS from the camera microcomputer 205 istransmitted from the camera microcomputer 205 to the lens microcomputer111 via a notification channel, which is a dedicated output channel forthe camera microcomputer 205.

As described above, the waiting-for-communication request BUSY from thelens microcomputer 111 is transmitted and received via the dedicatedoutput channel for the lens microcomputer 111, and the transmissionrequest signal RTS from the camera microcomputer 205 is transmitted andreceived via the dedicated output channel for the camera microcomputer205. This can shorten the communication disabled period between thecamera microcomputer 205 and the lens microcomputer 111. As a result, itis possible to increase the effective communication speed.

Regarding the start timing of communication, the transmission of datafrom the lens microcomputer 111 to the camera microcomputer 205 isstarted first. According to the detection of a start bit ST of a dataframe transmitted from the lens microcomputer 111, the cameramicrocomputer 205 starts transmitting data. The start timing ofcommunication is thus set, whereby it is possible to flexibly set thetiming when the lens microcomputer 111 having received the transmissionrequest signal RTS starts transmitting data to the camera microcomputer205.

For example, depending on the information processing capability of thelens microcomputer 111, it is possible to change the start timing of thetransmission of data. This can improve the communication speed betweenthe camera main body 200 and the interchangeable lens 100 withoutcausing the breakdown of communication.

<Issue Assumed in Present Exemplary Embodiment>

An issue assumed in the present exemplary embodiment is described.

If an attempt is made to display indices of distance information withouttaking into account the differences in specs between interchangeablelenses such as a wide angle lens and a telephoto lens, or thedifferences in specs between cameras, in specs such as the numbers ofpixels of display members of the cameras, an issue arises in thefollowing situation.

FIG. 19A illustrates representative index positions on a distance bartransmitted from the lens microcomputer 111 to the camera microcomputer205. More specifically, FIG. 19A illustrates a case where the displayposition of each index position is specified by the number of pixels.Positions 2001 to 2007 indicate start positions where representativeindices “0.45 m”, “0.6 m”, “0.8 m”, “1 m”, “1.5 m”, “3 m”, and “5 m” aredisplayed.

A position 2008 indicates a display origin position, and the displaystart position of “0.45 m” is indicated by the number of pixels countedfrom the display origin 2008, such as “30 pixels”. Similarly, thedisplay start position of “0.6 m” is indicated by the number of pixelscounted from the display origin 2008, such as “150 pixels”.

In this method, to effectively utilize the entire length of the distancebar, the lens microcomputer 111 of the interchangeable lens 100 needs tograsp in advance the number of pixels of the entire length of a displaymember of a camera to which the interchangeable lens 100 is attachable.

Further, if similar information is exchanged when the number ofeffective pixels of the display member of the camera increases, then asillustrated in FIG. 19B, the index positions are displayed closer toeach other than in FIG. 19A. In this case, there is a possibility thatit is difficult to recognize the boundary between “3 m” and “5 m” asillustrated at a position 2011, and “3 m” and “5 m” are erroneouslyrecognized as “35 m”.

To resolve such an issue, a technique is possible in which specs such asthe number of effective pixels of the display member of the camera aretransmitted to the lens, and the lens transmits object distanceinformation and representative index positions to the camera based onthe number of effective pixels of the display member of the camera.However, since the number of effective pixels of a camera to be releasedlater than the lens product cannot be known in advance, it is difficultto guarantee compatibility. Further, even if there is a wide variety ofitems to be displayed at the display unit of the camera, such as theobject distance information, representative index values, macromagnification information, and focusing range information, it isnecessary to prevent the items from influencing driving control of thefocus, the diaphragm, and the image stabilization. Further, if delayoccurs also in the communication of information for display, this causesdelay in the display and therefore reduces usability. Thus, it isnecessary to reduce the amount of communication regarding thecommunication of information for display.

In the present exemplary embodiment, not only does the lensmicrocomputer 111 transmit appropriate information to the cameramicrocomputer 205 based on the specs of the lens 100, but also the lensmicrocomputer 111 transmits a normalized value to the cameramicrocomputer 205, where necessary. Consequently, it is possible toappropriately display information corresponding to the interchangeablelens 100 at the camera display unit 206.

<Example of Display Screen Regarding Object Distance Information onDistance Bar>

Next, with reference to FIG. 8, a description will be given of anexample of a display screen of distance bar information on which objectdistance information regarding the lens 100 according to the presentexemplary embodiment is displayed at the camera display unit 206.

A live view display screen 801 is displayed at the camera display unit206.

An icon 802 indicates image capturing mode information regarding thecamera set in the menu of the camera. In this example, the imagecapturing mode information indicates a shutter speed priority mode.

Information display 803 relates to image capturing, such as the shutterspeed, the aperture value, the exposure setting value, and theInternational Organization for Standardization (ISO) sensitivity, asvarious pieces of setting information in the current imaging condition.

An object 804 indicates an object when an image is captured. In thestate where the object 804 is in focus, position information regardingthe focus lens 104 is communicated as object distance information fromthe lens microcomputer 111 to the camera microcomputer 205.

A distance bar 805 represents a distance area where an image can becaptured as the spec of the interchangeable lens 100, from the focusclosest side to the focus infinity side.

Values 806 are representative index values of distance information forfacilitating visual confirmation of the current object distanceinformation and are represented as, for example, “0.45 m”, “1.5 m”, and“5 m”. Such an index regarding the object distance is also referred toas a “first index”. The display positions of these representative indexvalues, the number of representative index values to be displayed, andthe display intervals between representative index values are changedbased on the specs (a wide angle lens or a telephoto lens) of theinterchangeable lens 100, whereby it is possible to obtain optimaldisplay quality.

A focus infinity position icon 807 indicates that the focus distance isinfinity. The focus infinity position icon 807 is also referred to as a“second index”. Generally, the interchangeable lens 100 is designed suchthat the focus lens position where a distant view is in focus is not atthe infinity side end of the physical range of movement of the focuslens 104, and allowance is provided beyond the infinity side end. Theamount of the allowance varies depending on the optical design of theinterchangeable lens 100. In the present exemplary embodiment, theallowance is referred to as an “over-infinity range”. The area from thedisplay position of the infinity icon 807 to the right end of the bar805 indicates the over-infinity range. As described above, the amount ofthe over-infinity range varies depending on the model of theinterchangeable lens 100. Thus, the display position of the infinityicon 807 changes based on the model of the interchangeable lens 100 tobe attached.

An icon 808 indicates the unit system of the currently displayed objectdistance information. For example, “m” indicates a meter, and “ft”represents a foot.

An index 809 indicates current position information regarding the focuslens 104, i.e., the object distance information in the state where thefocus lens 104 is in focus. In FIG. 8, the current position of the focuslens 104 is present near the index position of “1.5 m”. Thus, it ispossible to visually confirm that the focus distance is about 1.5 m.

A focus limit area 810 indicates an area where focus driving is limitedin a case where the focus limit switch 141 included in theinterchangeable lens 100 is enabled. The focus limit area 810illustrates an example where the focus limit switch 141 is switched to“0.8 m to ∞”. This represents that this area “closest to 0.8 m” is notused in autofocus. Generally, some interchangeable lens 100 includes afocus limiter SW that enables switching of the focus distance range ofautofocus. However, an area to be limited varies depending on the modelof the interchangeable lens 100. Thus, the focus limit area 810 can beswitched by acquiring the focus limit area 810 from the lensmicrocomputer 111 based on the model and the switch state of the lens100 to be attached.

Icons 811 and 812 indicate the driving direction of the focus lens 104.In a case where the focus is driven in the infinity direction, the icon811 is displayed, and the icon 812 is hidden. In a case where the focusis driven in the closest direction, the icon 811 is hidden, and the icon812 is displayed.

Depending on the interchangeable lens, the user can store in advance acertain focus lens position in a lens microcomputer included in theinterchangeable lens. For example, the user can operate a focus ring toa certain position of the focus ring corresponding to a desired focuslens position and store information corresponding to the focus lensposition. Then, for example, by operating an operation member providedin the interchangeable lens, the user can perform regeneration drivingof the focus lens to the stored focus lens position. The display screen801 may indicate that the regeneration driving is being performed. Forexample, the icon 811 or 812 may be displayed, thereby indicating thatthe focus lens 104 is being driven, and letting the user know thatregeneration driving is being performed. Further, for example, an icon(not illustrated) different from the icons 811 and 812 may be displayed.At this time, the information to be stored in the lens microcomputer mayonly need to be information corresponding to the focus lens position setin advance, and for example, the position of the focus ring may bestored.

An arrow 813 indicates the position where the representative indexposition of “0.6 m” is placed on the distance bar. The positioninformation is acquired from the lens microcomputer 111 throughcommunication and represented as a placement position of which thestarting point is the left end (i.e., the closest end) of the distancebar when the entire length of the distance bar is 100. For example, toplace the representative index position of “0.6 m” at a position of 10%from the left end of the distance bar relative to the entire length ofthe distance bar, information indicating that the index “0.6 m” isplaced at a normalized position “10” is acquired from the lensmicrocomputer 111. Although illustrated in the diagram for convenienceof description, the arrow 813 is not displayed on the actual live viewscreen 801. Similarly, arrows 814 and 815 are not displayed on the liveview screen 801, either.

Similar to the arrow 813, the arrow 814 indicates position informationregarding the current object distance position on the distance barnormalized with respect to the entire length of the distance bar 805that can be displayed at the camera display unit 206.

Similar to the arrow 813, the arrow 815 indicates position informationregarding the focus limit switch position on the distance bar normalizedwith respect to the entire length of the distance bar 805 that can bedisplayed at the camera display unit 206.

<Regarding Examples of Display Screen Regarding Macro MagnificationInformation and Depth-of-Field Information on Distance Bar>

While FIG. 8 illustrates an example where the object distanceinformation is displayed, then next, FIG. 9 illustrates examples ofdisplay in a case where information other than the object distanceinformation, such as the macro magnification information and thedepth-of-field information, is displayed.

A state 901 illustrates the state where the macro magnificationinformation is displayed in addition to the object distance information.Also in the magnification information, similar to the distanceinformation, representative index values and representative indexpositions are appropriately placed such that it is easy for the user tovisually confirm the representative index values and the representativeindex positions depending on the specs of the interchangeable lens 100.For example, an icon 902 indicates the position of a macro magnificationof 1.2 times. Based on position information normalized as the positionwhere “1.2×” is displayed as display information acquired from theinterchangeable lens 100 on the distance bar, “1.2×” is placed at aposition of “3”. Further, “0.7×” is placed at a position of “30” as anormalized position. The camera microcomputer 205 acquires suchinformation from the lens microcomputer 111 and displays the informationat the display unit 206.

A state 903 illustrates an example where the depth-of-field informationindicating an area in focus is displayed in addition to the currentobject distance information. The depth of field changes based on theaperture state. The smaller the aperture, the wider the depth of field.The depth of field is determined based onpermissible-circle-of-confusion information as the amount of blur, whichis a reference about whether the lens is in focus, and the aperturediameter. Thus, the camera microcomputer 205 acquires the depth-of-fieldinformation from the current aperture diameter information acquired fromthe lens microcomputer 111 and calculates the depth. For example, thecamera microcomputer 205 calculates an area in focus in a case where theaperture is set to F8 or F22. An index 809 is the current objectdistance information. An index 904 is an index position indicating thedepth-of-field area in a case where the aperture value is set to F8.0.On the distance bar, an icon 905 indicates that this index position isthe depth-of-field position when the aperture value is set to F8.0.Then, a range 906 indicates the depth-of-field area when the aperturevalue is set to F8.0. Similarly, an index 907 is an index positionindicating the depth-of-field area in a case where the aperture value isset to F22. On the distance bar, an icon 908 indicates that this indexposition is the depth-of-field position when the aperture value is setto F22. Then, a range 909 indicates the depth-of-field area when theaperture value is set to F22.

<Start Process>

Next, with reference to flowcharts for a camera start process in FIG.10, a steady operation process in FIG. 11A, and a display update processin FIG. 11B, a description will be given of the process of transmittingthe display information described with reference to FIGS. 8 and 9 fromthe interchangeable lens 100 to the camera main body 200 and displayingthe display information at the camera main body 200. First, withreference to FIG. 10, the camera start process will be described belowregarding both the processing of the camera microcomputer 205 and theprocessing of the lens microcomputer 111.

In steps S1001 and S1021, a negotiation communication process betweenthe camera main body 200 and the interchangeable lens 100 is performed.As the negotiation communication, the camera main body 200 transmits, tothe interchangeable lens 100, information regarding what functions thecamera main body 200 is compatible with. Conversely, the interchangeablelens 100 transmits, to the camera main body 200, function informationregarding functions included in the interchangeable lens 100. Morespecifically, the function information is, for example, informationregarding whether the interchangeable lens 100 has an imagestabilization function, or information regarding whether theinterchangeable lens 100 is compatible with the communication modes M2and M3 described with reference to FIGS. 4, 5A, 5B, and 5C.

In step S1002, the camera microcomputer 205 determines whether, as aresult of the communication process in steps S1001 and S1021,communication in the communication mode M2 can be performed by thecombination of the camera microcomputer 205 and the interchangeable lens100 currently attached to the camera microcomputer 205. In the presentexemplary embodiment, if communication in the communication mode M2cannot be performed, a process for displaying the object distanceinformation in the camera is not performed. Thus, the cameramicrocomputer 205 shifts to a steady state. This is because theeffective communication rate is higher in the communication mode M2 thanin the communication mode M1, and therefore, there is room in thecommunication band so long as the communication mode M2 is selected.However, even if the combination of the camera microcomputer 205 and theinterchangeable lens 100 is incompatible with the communication mode M2and the communication mode M1 is selected, the process for displayingthe object distance information in the camera may be performed bydevising a method such as thinning the communication frequency based onthe room in the communication band. If it is determined thatcommunication in the communication mode M2 can be performed (Yes in stepS1002), then in steps S1003 and S1022, a process for switching to thecommunication mode M2 is performed. The switching process is performedby the method described above with reference to FIG. 6.

The process will be described below in which the camera main body 200acquires information for displaying the object distance information fromthe interchangeable lens 100 through communication. Terms are defined asfollows. Information that is finalized when the interchangeable lens 100is attached to the camera main body 200 (e.g., the focal length at thetelephoto end and the wide-angle end and the representative indexpositions of the object distance information) is referred to as “staticdisplay information”. The static display information is information thatdoes not change depending on the states of the camera main body 200 andthe interchangeable lens 100, such as operations on the camera and thelens and the image capturing mode. On the other hand, displayinformation that dynamically changes depending on the operation of thecamera 200, such as the position of the focus, is referred to as“dynamic display information”. The dynamic display information isinformation that changes depending on the states of the camera main body200 and the interchangeable lens 100, such as operations on the cameraand the lens and the image capturing mode. The static displayinformation is also referred to as “first information”. The dynamicdisplay information is also referred to as “second information”.

In step S1004, the camera microcomputer 205 requests from theinterchangeable lens 100 the data size of the static display informationthat is required to display the object distance information. Adescription is given of the static display information that is requiredto display the object distance information.

The static display information for displaying the object distanceinformation at the display unit 206 of the camera includes informationcorresponding to the presence or absence of an operation member of theinterchangeable lens 100, and information regarding the display ofindices. Specifically, the static display information according to thepresent exemplary embodiment is, for example, the following parameters 1to 12.

The Information Corresponding to the Presence or Absence of an OperationMember

1. the presence or absence of a selection switch for switching to amacro imaging state2. the presence or absence of a focus limit switch

The Information Regarding the Display of Indices

3. the number of representative index positions represented in meters4. the numerical values of representative indices represented in meters(as many as the number of representative index positions)5. normalized placement position information regarding representativeindices on the distance bar represented in meters (as many as the numberof representative index positions)6. the number of representative index positions represented in feet7. the numerical values of representative indices represented in feet(as many as the number of representative index positions)8. normalized placement position information regarding representativeindices on the distance bar represented in feet (as many as the numberof representative index positions)9. the number of representative index positions represented by macromagnification10. the numerical values of representative indices represented by macromagnification (as many as the number of representative index positions)11. normalized placement position information regarding representativeindices on the distance bar represented by macro magnification (as manyas the number of representative index positions)12. normalized placement position information regarding an “∞” mark onthe distance bar

The static display information is described using the example of displayin FIG. 8.

First, “the information corresponding to the presence or absence of anoperation member” is described. The information is information used toindicate that the interchangeable lens 100 has a function correspondingto an operation member. Thus, another piece of information can also beused instead of the information so long as the information correspondsto the presence or absence of a function regarding display. That is, forexample, the information “1. the presence or absence of a selectionswitch for switching to a macro imaging state” may only need to beinformation indicating that the interchangeable lens 100 enablesswitching to a macro imaging state. Further, “2. the presence or absenceof a focus limit switch” may only need to be information indicating thatthe interchangeable lens 100 has the function of limiting the rangewhere the focus lens 104 is moved.

Regarding “1. the presence or absence of a selection switch forswitching to a macro imaging state”, there is an interchangeable lensproduct that switches to a macro imaging mode by, as an operation on alens barrel, e.g., operating a switch (not illustrated) in the barrelwhile hitting a zoom ring against the switch. This item indicateswhether the interchangeable lens 100 includes such a selection switchfor switching to a macro imaging state. In this proposal, when macroimaging is performed, the imaging magnification is displayed at thedisplay unit 206 of the camera. Thus, the display content can beswitched by operating the switch. If the static display informationindicates that the switch is not present, communication control may beperformed not to acquire display information when macro imaging isperformed.

Regarding “2. the presence or absence of a focus limit switch”, there isan interchangeable lens product including in a lens barrel a focus limitswitch for limiting the distance range where the lens can be broughtinto focus. In this proposal, the limit state of the focus limit switchis displayed at the display unit 206 of the camera. If the staticdisplay information indicates that the switch is not present,communication control may be performed not to acquire displayinformation regarding the index position of the focus limit switch.

In the example of FIG. 8, since seven representative index positions,i.e., “0.45 m”, “0.6 m”, “0.8 m”, “1 m”, “1.5 m”, “3 m”, and “5 m”, areplaced, the parameter “3. the number of representative index positionsrepresented in meters” is “7”.

As will be described below with reference to FIG. 10, the informationregarding the above terms 1 to 12 is collectively acquired when the lens100 is attached. At this time, if the number of representative indexvalues is a fixed value, and if the number of representative indexvalues is not the maximum number, it is necessary to provide blank inthe communication content. On the other hand, the number ofrepresentative index positions is included in the communication contentas described above. Thus, the camera having received this informationanalyzes the order of pieces of reception data based on the number ofrepresentative index positions, thereby extracting the informationregarding the terms 1 to 12. This eliminates the need to performcommunication leading to unnecessary blank. More specifically, if theparameter “3. the number of representative index positions representedin meters” is “7”, reception data is received in the following order.

The first byte: the presence or absence of a selection switch forswitching to a macro imaging stateThe second byte: the presence or absence of a focus limit switchThe third byte: the number of representative index positions representedin metersThe fourth to tenth bytes: the numerical values of representativeindices represented in meters (in a case where a single index value isrepresented in one byte)The eleventh to seventeenth bytes: normalized placement positioninformation regarding representative indices on the distance barrepresented in meters (in a case where a single index value isrepresented in one byte)

The number of representative index positions is thus included in thecommunication content, whereby it is possible to communicate pieces ofdata without intervals.

“4. the numerical values of representative indices represented in meters(as many as the number of representative index positions)” are “0.45”,“0.6”, “0.8”, “1”, “1.5”, “3”, and “5”.

Then, regarding “5. normalized placement position information regardingrepresentative indices on the distance bar represented in meters (asmany as the number of representative index positions)”, valuesnormalized with respect to a predetermined range (length) of thedistance bar (an example of a display area) displayed at the displayunit 206 are communicated. The lens microcomputer 111 has informationregarding where on the distance bar the representative index positionsare to be placed. For example, as information regarding where on thedistance bar the representative index position of “0.6 m” is to beplaced, a value normalized when the entire length of the distance bar is100 is communicated. The predetermined range (length) as a reference maybe defined in advance by the camera microcomputer 205 and the lensmicrocomputer 111, or may be acquired through communication. “0.45 m” isplaced at a position of “3” as a normalized value from the closest end.“0.6 m” is placed at a position of “15” as a normalized value from theclosest end. As the length of the arrow 813 represented in FIG. 8, avalue of “15” is set to the parameter.

This display position information can be determined from the viewpointof the specs and the design of the interchangeable lens 100. Forexample, to display the index “0.45 m” as the imaging-possible distance(the shortest focus distance) of the interchangeable lens 100 anddisplay the index “5 m” before the “∞” mark on the infinity side, thenbased on how much display space the user wishes to provide further onthe closest side than “0.45 m” and between “5 m” and the “∞” mark as adesign in addition to a portion between “0.45 m” to “5 m”, positioninformation regarding the index values can be determined within anormalized value of 100.

Also in the cases of the foot representation and the macro magnificationrepresentation, the index values are similarly communicated asnormalized values.

If attention is paid to 3, 4, and 5, “3. the number of representativeindex positions represented in meters” is information corresponding tothe number of indices. Further, “4. the numerical values ofrepresentative indices represented in meters (as many as the number ofrepresentative index positions)” are pieces of information correspondingto numerical values to be displayed corresponding to as many indices asthe number indicated by the information corresponding to the number ofindices. Furthermore, “5. normalized placement position informationregarding representative indices on the distance bar represented inmeters (as many as the number of representative index positions)” isinformation corresponding to the positions where the pieces ofinformation corresponding to the numerical values are displayed. Asdescribed above, information corresponding to the number of indices,pieces of information corresponding to numerical values to be displayedcorresponding to as many indices as the number indicated by theinformation corresponding to the number of indices, and informationcorresponding to the positions where the pieces of informationcorresponding to the numerical values are displayed form a set.

Also regarding 6, 7, and 8, the lens microcomputer 111 has the above setof pieces of information in the foot representation, which is a unitsystem different from the meter representation.

Further, also regarding 9, 10, and 11, the lens microcomputer 111 hasthe above set of pieces of information in the macro magnificationrepresentation, which is a unit system different from the meterrepresentation and the foot representation.

As described above, regarding information that varies depending on theunit system, the lens microcomputer 111 has information with respect toeach unit system.

“12. normalized placement position information regarding an “∞” mark onthe distance bar”, i.e., the placement position of the “∞” mark in FIG.8, is the same on the distance bar in any of the meter representation,the foot representation, and the macro magnification representation.Thus, the parameter may only need to have a single common value.

The above parameters are not dynamically changed. Thus, when the cameramain body 200 to which the interchangeable lens 100 is attached starts(or at the timing when the interchangeable lens 100 is attached to thecamera main body 200 in the state where the camera is operating), theparameters are acquired. In step S1004, the camera microcomputer 205inquires of the interchangeable lens 100 about the data size ofcommunication data of the static display information. This is becausethe number of representative indices changes depending on the specs ofthe interchangeable lens 100, and this is also to finalize thecommunication size in advance to communicate all the static displayinformation in the communication mode M3, where the effectivecommunication rate is higher.

In step S1023, the lens microcomputer 111 generates the static displayinformation to be displayed at the display unit 206 of the camera mainbody 200 and responds to the camera microcomputer 205 with the data sizeof the static display information.

In steps S1005 and S1024, to collectively acquire the static displayinformation at high speed, the communication mode is switched to thecommunication mode M3 described in FIGS. 5A, 5B, and 5C, where theeffective communication speed is the highest. In the communication modeM3, the data communication directions of the communication terminals areswitched. Thus, the directions of internal buffers are switched in ordersuch that collision of data communication does not occur. Thus, aprocess for switching the communication mode is required. Although ittakes a certain processing time to perform the switching process, it ispossible to shorten the communication time in a case where the amount ofcommunication is somewhat large. Conversely, if the communication modeM3 is used in a case where the amount of communication is small, theprocess for switching the communication mode results in overhead,thereby lengthening the communication processing time. Since the datasize of the static display information is somewhat large in this case,it is possible to shorten the communication time using the communicationmode M3.

In step S1006, the camera microcomputer 205 communicates an acquisitionrequest command to acquire the static display information. In stepS1025, the lens microcomputer 111 having received the communicationcommand performs a process for normalizing the static displayinformation, which has been generated in step S1023, to be displayed atthe display unit 206 of the camera. The normalization process may onlyneed to be performed, for example, after the camera microcomputer 205asserts the signal RTS and by the time when the data DLC is transmittedin FIGS. 5A, 5B, and 5C. Alternatively, the normalization process may beperformed simultaneously with the data generation process in step S1023.

In step S1026, the lens microcomputer 111 communicates data subjected tothe process for normalizing the static display information to the cameramicrocomputer 205 through the DLC communication channel. In step S1007,the camera microcomputer 205 receives the data.

In steps S1008 and S1027, the communication mode returns to thecommunication mode M2. This is because in the processes of steps S1006,S1007, S1025, and S1026, the camera microcomputer 205 completes thecommunication of a large amount of data (e.g., the above items 1 to 13)required to display static lens information that does not dynamicallychange.

In step S1009, the camera microcomputer 205 transmits the normalizedstatic display information to a block (not illustrated) for controllingthe camera display unit 206.

In step S1010, the camera microcomputer 205 determines whether thedisplay of the distance information is set to “enabled” in the settingof the camera menu. If the display setting is disabled (No in stepS1010), it is not necessary to display the distance information untilthe menu is set to “the display setting is enabled” again. Thus, thecamera microcomputer 205 shifts to a steady state. If the displaysetting is enabled in the menu (Yes in step S1010), then in step S1011and after that, the processing proceeds to a process for communicatingand displaying the object distance information that dynamically changes.

A description is given of the dynamic display information that isrequired to display the object distance information.

The dynamic display information is information required to change thedisplay state based on the state of an operation member of the cameramain body 200 or the interchangeable lens 100. In the present exemplaryembodiment, the dynamic display information is, for example, thefollowing parameters.

Information Regarding Whether Display is to be Performed

1. whether the object distance information is to be displayed or hidden

Information Corresponding to a Position

2. normalized position information regarding the current object distanceon the distance bar3. normalized position information regarding the focus limit on theinfinity end side on the distance bar4. normalized position information regarding the focus limit on theclosest end side on the distance bar5. normalized position information regarding the macro area on thedistance bar

First, the “information regarding whether display is to be performed” isdescribed. For example, the lens microcomputer 111 notifies the cameramicrocomputer 205 of the information “1. whether the object distanceinformation is to be displayed or hidden” in a case where the objectdistance information should be hidden. For example, to avoid showing theuser uncomfortable display in a case where the driving of the focus lens104 of the interchangeable lens 100 enters an irregular state, such aswhere the driving of the focus lens 104 steps out, the lensmicrocomputer 111 communicates “hidden” to the camera microcomputer 205.As another exemplary embodiment, the lens microcomputer 111 maycommunicate not “hidden” but “stop an update from the previous displaystatus” to the camera microcomputer 205. A configuration may be employedin which “the information regarding whether display is to be performed”further includes “whether information regarding the driving state of thefocus lens is to be displayed or hidden”. This information iscommunicated, whereby it is possible to display the icons 811 and 812indicating the driving direction of the focus lens 104. At this time,information regarding the driving direction of the focus lens 104 mayalso be transmitted from the lens microcomputer 111 to the cameramicrocomputer 205, where necessary. Alternatively, “whether informationregarding the driving state of the focus lens in the infinity directionis to be displayed or hidden” and “whether information regarding thedriving state of the focus lens in the closest direction is to bedisplayed or hidden” may be transmitted as different pieces ofinformation. Further, in a configuration in which an icon is separatelydisplayed in a case where the above regeneration driving is performed,“whether the icon regarding regeneration driving is to be displayed orhidden” may be transmitted from the lens microcomputer 111 to the cameramicrocomputer 205.

Next, the “information corresponding to a position” is described. “2.normalized position information regarding the current object distance onthe distance bar” is a parameter indicating a display positionnormalized with respect to the entire length of the distance bar in FIG.8 and corresponds to the arrow 814. The lens microcomputer 111 canacquire absolute position information regarding focus pulses based onoutput information regarding the focus position detection sensor 140.The lens microcomputer 111 calculates the current focus pulse positionas a normalized value from the absolute position information regardingfocus pulses and position information regarding a pulse encoder from theclosest side to the infinity side.

“3. normalized position information regarding the focus limit on theinfinity end side on the distance bar” is a parameter indicating adisplay position normalized with respect to the entire length of thedistance bar in FIG. 8 and corresponds to the arrow 815.

In step S1011, the camera microcomputer 205 communicates to the lensmicrocomputer 111 an acquisition request command to acquire the displayinformation that dynamically changes.

In step S1028, the lens microcomputer 111 generates the displayinformation that dynamically changes. Then, the lens microcomputer 111performs a process for normalizing the display information. In stepS1029, the lens microcomputer 111 responds to the camera microcomputer205 with the normalized display information as a communication result.In step S1012, the camera microcomputer 205 receives this responseresult.

In step S1013, the camera microcomputer 205 transmits the displayinformation that dynamically changes and is acquired in step S1012, asinformation for initially displaying the object distance information tothe camera display unit 206.

A description is given of the significance of communicating the staticdisplay information in the communication mode M3 and communicating thedynamic display information in the communication mode M2.

The above processing achieves the communication and display process whenthe camera starts, and then achieves the initial display state as in theexample illustrated in FIG. 8.

<Steady Operation Process>

Next, with reference to flowcharts in FIGS. 11A and 11B, a descriptionis given of a process for updating the display of the object distanceinformation when the camera is in the steady state.

FIG. 11A is a flowchart illustrating the processing of the camera mainbody 200 and the processing of the interchangeable lens 100 regardingthe display of the object distance information. The processing isexecuted by a program recorded in the camera microcomputer 205. Theprocess for displaying the information is described regarding both theprocesses of the lens communication control unit 110 that communicateswith the interchangeable lens 100, and the processing of the cameradisplay unit 206 that performs the display process.

First, the processing of the camera display unit 206 is described.

In steps S1101 and S1121, as described in the start process in FIG. 10,the static display information and the dynamic display information asinitial values for display from the interchangeable lens 100 aretransmitted from the lens communication control unit 110 to the cameradisplay unit 206.

In step S1102, the camera display unit 206 determines which of “asetting for displaying” the object distance information and “a settingfor not displaying” the object distance information is made as the stateof the menu of the camera. If “a setting for not displaying” the objectdistance information is made (No in step S1102), this display process isnot performed. Thus, the camera display unit 206 waits for the settingof the menu to be changed. If “a setting for displaying” the objectdistance information is made (Yes in step S1102), the processingproceeds to step S1103.

In step S1103, the camera display unit 206 displays the static displayinformation and the dynamic display information as initial valuesacquired from the lens communication control unit 110 in step S1101. Thepositions of the representative index values 806 and the current objectdistance position 809 of these pieces of display information arerelative positions in a case where the entire length of the focusdistance bar is 100. More specifically, in a case where the displayposition of the representative index value “0.8” of the focus distanceis “20”, the representative index value “0.8” is displayed at a positionof 100 pixels relative to the entire length of the focus distance bar,i.e., 500 pixels.

In step S1104, to determine whether the display of the dynamic displayinformation is to be updated as the subsequent processing, the cameradisplay unit 206 reconfirms the display setting. After a display updateprocess in step S1107 is performed, then in this step, it is determinedwhether the display update process is to be continued.

In step S1105, the camera display unit 206 determines whether anotification for clearing the static and dynamic display information isgiven by the lens communication control unit 110. If a clearingnotification for clearing the display is given (Yes in step S1105), thenin step S1106, the camera display unit 206 clears the display state ofthe display unit 206. In step S1108, the camera display unit 206 waitsfor the static display information to be transmitted from the lenscommunication control unit 110 again. A notification for clearing thedisplay is not given (No in step S1105), the proceeding proceeds to thedisplay update process in step S1107. This process will be describedbelow with reference to a subroutine in FIG. 11B.

Next, the processing of the communication control unit 110 of theinterchangeable lens 100 will be described.

In step S1121, the communication control unit 110 transmits the staticdisplay information and the dynamic display information as initialvalues to the camera display unit 206.

In step S1122, the communication control unit 110 determines whether theinterchangeable lens 100 is detached. If the interchangeable lens 100 isdetached (Yes in step S1122), the communication control unit 110transmits a notification for clearing the static and dynamic displayinformation to the camera display unit 206. This is because when thelens is detached, it is necessary to hide the display of the cameradisplay unit 206, and then, if another interchangeable lens 100 isattached, it is necessary to perform display based on the specs of theattached interchangeable lens 100.

In step S1124, the communication control unit 110 waits until the cameramicrocomputer 205 confirms the state where the lens is attached in thecommunication I/F circuit 208.

In step S1125, the initial communication process between the cameramicrocomputer 205 and the lens microcomputer 111 described in FIG. 10 isperformed. By this process, the static display information and thedynamic display information as initial values corresponding to the specsof the interchangeable lens 100 are acquired, and the process fordisplay from step S1121 is performed again.

If the lens 100 continues to be attached in step S1122 (No in stepS1122), the processing proceeds to step S1126. In step S1126, thecommunication control unit 110 determines whether it is necessary toupdate the object distance information regarding the interchangeablelens 100. For example, while the menu is being displayed, and if thedistance bar for displaying the object distance is not displayed, thedetermination is “No” (No in step S1126), and the processing proceeds tostep S1128. If it is determined that it is necessary to update thedisplay (Yes in step S1126), the processing proceeds to step S1127. Instep S1127, the communication control unit 110 performs a process foracquiring the dynamic display information from the interchangeable lens100 and transmits the dynamic display information to the camera displayunit 206. If, however, it is not necessary to update the display (No instep S1126), the processing proceeds to step S1128. In step S1128, thecommunication control unit 110 does not perform a communication processwith the interchangeable lens 100.

With reference to a timing chart of a communication process in FIG. 12,the communication process in steps S1127 and S1128 is described.

FIG. 12 is a timing chart of a lens communication control processperformed between the camera microcomputer 205 and the lensmicrocomputer 111, where the horizontal axis represents the lapse oftime, and the vertical axis represents communication items. In thiscase, communication control during live view is illustrated as anexample. Alternatively, viewfinder imaging may also be used.

An imaging synchronization signal 1201 indicates the start timing ofaccumulation control 1202 of the image sensor 201. The imagingsynchronization signal 1201 is generated in a cycle corresponding to theframe rate. For example, if control is performed at 60 fps, a verticalsynchronization signal 1210 is input to the camera microcomputer 205 ina cycle of 16.6 ms. A timing 1211 indicates the center-of-gravity timingof the accumulation control 1202 of the image sensor 201.

An item 1203 indicates synchronization signal communication for sharingthe exposure timing between the camera main body 200 and theinterchangeable lens 100. The communication is performed using thevertical synchronization signal 1210 as a trigger. In each communicationprocess illustrated in FIG. 12, a process indicated by a shaded portionindicates a communication process in which there is a timingrestriction. If delay occurs in a synchronization signal communicationprocess 1220, there is a difference in the recognition of the exposuretiming between the camera microcomputer 205 and the lens microcomputer111. Thus, it is necessary to execute communication based on apredetermined timing restriction. Communication for displaying theobject distance information achieved by the present exemplary embodimentneeds to be performed so as not to influence such a communicationprocess in which there is a timing restriction.

An item 1204 is a communication process for an image stabilizationfunction in which the camera microcomputer 205 and the lensmicrocomputer 111 operate in conjunction with each other. For example,an example is illustrated where two communication processes 1221 and1222 are performed with regard to one frame. There is a timingrestriction in which the communication 1222 is performed before or at apredetermined timing with the center-of-gravity timing 1211 of theaccumulation control 1202 of the image sensor 201 as the starting point.

An item 1205 is a communication process for autofocus control. Forexample, a process 1223 is communication for acquiring from theinterchangeable lens 100 a parameter for correcting a defocus amount orthe current state information regarding the focus lens 104. For example,a process 1224 is communication in which the camera microcomputer 205requests the lens microcomputer 111 to drive the focus ring forfocusing.

An item 1206 is a communication process for automatic exposure (AE)control. For example, a process 1225 is communication for acquiring fromthe interchangeable lens 100 the current optical information such as theaperture diameter value used for exposure control. A process 1226 iscommunication in which the camera microcomputer 205 requests the lensmicrocomputer 111 to drive the diaphragm.

An item 1207 is a data communication process for displaying the objectdistance and is communication for acquiring from the interchangeablelens 100 the display information that dynamically changes. Ideally, asillustrated in FIG. 12, all the communication processes should beperformed in one frame. However, in a case where there is no room in thecommunication band, for example, data communication for AE is scheduledto be performed every two frames. In the present exemplary embodiment,an example has been described where the dynamic display information isperiodically communicated. The present disclosure, however, is notlimited to this so long as, if the dynamic display information changes,display according to the change can be performed. For example, the lensmicrocomputer 111 may detect that the dynamic display informationchanges. Then, according to the detection, the lens microcomputer 111may notify the camera microcomputer 205 that a change in the dynamicdisplay information is detected, thereby communicating the dynamicdisplay information only if necessary.

Next, with reference to FIG. 11B, a description is given of a displayupdate process of the camera display unit 206 in step S1107.

In step S1140, the camera display unit 206 determines a timeout statusin a case where the display state of the object distance is set tohidden based on a timer. This mode will be described below in stepS1146. If, as a result of the determination of whether the display is tobe maintained based on a timeout, the display is to be maintained (No instep S1140), the processing proceeds to step S1142. If it is determinedthat the display is to be hidden (Yes in step S1140), the processingproceeds to step S1154.

In step S1142, the camera display unit 206 determines the setting statusof a display menu regarding how to display information. In the presentexemplary embodiment, in the menu, the display pattern of the objectdistance information can be set among “always display when MF isperformed”, “display for predetermined time when focus is adjusted”,“always display”, and “not display”. If the display setting of the menuis “always display when MF is performed”, the processing proceeds tostep S1143. If the display setting of the menu is “display forpredetermined time when focus is adjusted”, the processing proceeds tostep S1146. If the display setting of the menu is “always display”, theprocessing proceeds to step S1149. If the display setting of the menu is“not display”, this subroutine ends.

In step S1143, the camera microcomputer 205 determines which of an AFstate and an MF state the interchangeable lens 100 notifies the cameramicrocomputer 205 of as the state of a lens focus switch provided in thelens barrel. As another exemplary embodiment, in a form in which the AFstate and the MF state are switched in the camera menu, the cameramicrocomputer 205 may confirm the setting state of the menu. If thestate is the AF state (No in step S1143), the processing proceeds tostep S1151. If the state is the MF state (Yes in step S1143), theprocessing proceeds to step S1144.

In step S1144, based on the latest dynamic display information, thecamera microcomputer 205 performs a display update process for updatingthe display of the object distance information (distance barinformation) at the display unit 206.

In step S1146, the camera microcomputer 205 clears the timer for erasingthe display of the object distance using a bar.

The process of step S1147 is similar to that of step S1144.

In step S1148, to hide the distance bar for the object distanceinformation in a predetermined time, the camera microcomputer 205 setsthe timer for erasing the object distance information.

If the setting of the menu is assigned to “always display” in stepS1142, the processing proceeds to step S1149. The processing content ofstep S1149 is similar to that of step S1144.

If the display setting of the menu is a setting other than “notdisplay”, then in step S1151, the camera microcomputer 205 makes adetermination to notify the user that the focus is at the closest end orthe infinity end.

More specifically, the camera microcomputer 205 determines the“normalized position information regarding the current object distanceon the distance bar” included in the dynamic display information. If theposition information indicates the closest end position, the processingproceeds to step S1152. If the position information indicates theinfinity end position, the processing proceeds to step S1153. If theposition information indicates neither the closest end nor the infinityend, this subroutine ends.

In step S1152, the camera microcomputer 205 changes the color of thefocus moving direction icon 812 to gray. This causes the user torecognize that the focus will not change even if the focus ring isrotated further to the closest side when the manual focus operation isperformed.

In step S1153, the camera microcomputer 205 changes the color of thefocus moving direction icon 811 to gray. This causes the user torecognize that the focus will not change even if the focus ring isrotated further to the “∞” side when the manual focus operation isperformed.

If it is determined in step S1140 that the display state of the objectdistance is set to hidden based on the timer (Yes in step S1140), theprocessing proceeds to step S1154. In step S1154, the cameramicrocomputer 205 hides the various pieces of object distanceinformation described in FIG. 8.

By the above communication method between the imaging apparatus and theaccessory device and the above display process by the imaging apparatus,the position where information regarding the object distance informationto be displayed in the imaging apparatus is displayed is transmitted asa normalized numerical value to the imaging apparatus throughcommunication. Consequently, no matter what imaging apparatus theaccessory devices different in specs are attached to, it is possible toperform optimal display.

Further, data regarding scale display for displaying the object distanceinformation is acquired when the accessory device is attached. Then, ina steady state, only the object distance information regarding theaccessory device that dynamically changes is acquired, therebyminimizing the communication load. This reduces the influence on varioustypes of control such as AF control, AE control, and image stabilizationcontrol and also enables communication for displaying an object to beperformed frequently, such as every vertical signal timing. Thus, it ispossible to perform various types of driving control and achieve thedisplay of the object distance information without delay in the display.

In the first exemplary embodiment, a description has been given of acase where the object distance information detected by the lensmicrocomputer 111 is displayed at the display unit 206 of the cameramain body 200, and a case where the macro magnification information orthe depth-of-field information is further displayed. In a secondexemplary embodiment, a case is described where the camera microcomputer205 acquires through communication the camera shake state informationobtained by the shake sensor of the vibrating gyroscope and detected bythe lens microcomputer 111 and displays the camera shake stateinformation at the display unit 206.

Various components of the camera main body 200 and the interchangeablelens 100, a start process, and a communication process in a steady stateare similar to those in the first exemplary embodiment, and thereforeare not described here.

In the display of the camera shake information achieved in the presentexemplary embodiment, the present exemplary embodiment is different fromthe first exemplary embodiment in items communicated as the dynamicdisplay information and the static display information and controlregarding display. Thus, these differences are described.

In the present exemplary embodiment, in addition to the static displayinformation described in the first exemplary embodiment, as staticdisplay information for displaying a camera shake status, the lensmicrocomputer 111 transmits the following information to the cameramicrocomputer 205.

1. the presence or absence of a vibrating gyroscope in theinterchangeable lens 100

That is, the camera microcomputer 205 transmits information indicatingthat the camera microcomputer 205 has the function of detecting thecamera shake status, as information corresponding to the presence orabsence of a function, to the lens microcomputer 111.

Then, in the present exemplary embodiment, information to be acquired asthe dynamic display information is switched depending on the displaytarget. If the display target is the “camera shake status”, the lensmicrocomputer 111 transmits the following information as the dynamicdisplay information to the camera microcomputer 205.

1. the vibration detection value in the pitch direction of the vibratinggyroscope

2. the vibration detection value in the yaw direction of the vibratinggyroscope

That is, the lens microcomputer 111 transmits detection values obtainedby detecting the camera shake status to the camera microcomputer 205.If, on the other hand, the display target is not the “camera shakestatus”, the lens microcomputer 111 transmits the static displayinformation described in the first exemplary embodiment to the cameramicrocomputer 205.

First, with reference to FIG. 13, the display content of the camerashake status is described.

A state 1301 illustrates an example where the detection status of thecurrent camera shake amount is displayed. In the information display,the camera microcomputer 205 acquires through communication the camerashake state information obtained by the shake sensor of the vibratinggyroscope of the interchangeable lens 100 and displays the camera shakestate information at the display unit 206. A state 1302 indicates thevibration status in the pitch direction, and a gauge 1303 indicates thevibration level. Similarly, a state 1304 indicates the vibration statusin the yaw direction, and a gauge 1305 indicates the vibration level.

Next, a control flow for display will be described.

The present exemplary embodiment is similar to the first exemplaryembodiment in the flow of the start process described with reference toFIG. 10 and the flow of the steady operation process described withreference to FIG. 11A, except for step S1127 in the communicationprocess of the interchangeable lens 100 and step S1107 in the processingof the camera display unit 206. Thus, the similar portions are notdescribed here. With reference to FIG. 14, a description is given of asubroutine process of the display update process of the camera displayunit 206 in step S1107.

If the subroutine in step S1107 is started, then in step S1401, thecamera display unit 206 determines a timeout status in a case where thedisplay state of the camera shake status is set to hidden based on atimer. This mode will be described below in step S1406.

In step S1402, the camera display unit 206 determines whether a targetto be displayed at the display unit 206 is the “camera shake status” inthe setting of the menu of the camera. If a display menu is set to the“camera shake status” (Yes in step S1402), then in step S1403, thecamera display unit 206 further determines the setting status of adisplay menu regarding how to display information. Similar to the firstexemplary embodiment, the display pattern of the camera shake status canbe set among “always display when MF is performed”, “display forpredetermined time when focus is adjusted”, “always display”, and “notdisplay”.

If the display setting of the menu is “always display when MF isperformed”, the processing proceeds to step S1404. If the displaysetting of the menu is “display for predetermined time when focus isadjusted”, the processing proceeds to step S1406. If the display settingof the menu is “always display”, the processing proceeds to step S1409.If the display setting of the menu is “not display”, the subroutineends.

In step S1404, the camera microcomputer 205 determines which of the AFstate and the MF state the interchangeable lens 100 notifies the cameramicrocomputer 205 of as the state of the lens focus switch provided inthe lens barrel. As another exemplary embodiment, in a form in which theAF state and the MF state are switched in the camera menu, the cameramicrocomputer 205 may confirm the setting state of the menu. If thestate is the AF state (No in step S1404), the subroutine ends. If thestate is the MF state (Yes in step S1404), then in step S1405, thecamera microcomputer 205 displays the camera shake status.

In step S1406, the camera microcomputer 205 clears the timer for erasingthe camera shake status.

The process of step S1407 is similar to that of step S1405.

In step S1408, to hide the camera shake status in a predetermined time,the camera microcomputer 205 sets the timer for erasing the camera shakestatus.

If the setting of the menu is assigned to “always display” in stepS1403, the processing proceeds to step S1409. The processing content ofS1409 is similar to that of step S1405.

If the camera shake status display timer times out in step S1401 (Yes instep S1401), then in step S1410, the camera microcomputer 205 hides thecamera shake status.

If the display item is not the “camera shake status” in step S1402 (Noin step S1402), then in step S1411, the camera microcomputer 205proceeds to the process for displaying the object distance informationdescribed in the first exemplary embodiment.

Next, with reference to FIG. 15, a lens communication control unitprocess according to the present exemplary embodiment will be described.As described above, however, processes are similar to those in the firstexemplary embodiment except for step S1127.

If it is determined in step S1126 that it is necessary to update thedisplay in the camera state (Yes in step S1126), the processing proceedsto step S1501.

In step S1501, the lens communication control unit 110 determineswhether a target to be displayed is the “camera shake status” in themenu of the camera. If the display target is the “camera shake status”(Yes in step S1501), then in step S1502, the lens communication controlunit 110 sets the dynamic display information to be acquired from thelens microcomputer 111 to the following values required to display the“camera shake status”.

1. the vibration detection value in the pitch direction of the vibratinggyroscope

2. the vibration detection value in the yaw direction of the vibratinggyroscope

If the display target is not the “camera shake status” but the “objectdistance information” (No in step S1501), then in step S1503, the lenscommunication control unit 110 sets information to be acquired from thelens microcomputer 111 to the following information required to displaythe object distance information described in the first exemplaryembodiment.

1. whether the object distance information is to be displayed or hidden

2. normalized position information regarding the current object distanceon the distance bar

3. normalized position information regarding the focus limit on theinfinity end side on the distance bar

4. normalized position information regarding the focus limit on theclosest end side on the distance bar

5. normalized position information regarding the macro area on thedistance bar

More specifically, a communication command to acquire the “camera shakestatus” and a communication command to acquire the “object distanceinformation” are defined and appropriately used based on the cameramenu.

As described above, in the present exemplary embodiment, data regardingscale display for displaying the object distance information that variesdepending on the specs of the accessory device and information requiredto display the camera shake status are acquired when the accessorydevice is attached. Further, then, in a steady state, the objectdistance information regarding the accessory device that dynamicallychanges and the information regarding the camera shake status areexclusively acquired. Consequently, in a steady operation, onlyparameters that dynamically change and are required for display arecommunicated. This reduces the amount of use of the communication bandand minimizes the system load, whereby it is possible to prevent delayin the acquisition of display information from the accessory device.

In the first exemplary embodiment, a description has been given of acase where the object distance information detected by the lensmicrocomputer 111 is displayed at the display unit 206 of the cameramain body 200, and a case where the macro magnification information orthe depth-of-field information is further displayed. In a thirdexemplary embodiment, a case is described where, if the interchangeablelens 100 is a zoom lens, the camera microcomputer 205 acquiresinformation regarding the zoom position through communication anddisplays the information at the display unit 206.

Various components of the camera main body 200 and the interchangeablelens 100, a start process, and a communication process in a steady stateare similar to those in the first exemplary embodiment, and thereforeare not described here. To display the zoom position, however, someitems are be additionally acquired as static display information.

That is, in addition to the above items described in the first exemplaryembodiment, the lens microcomputer 111 also transmits the followingitems to the camera microcomputer 205.

13. the number of representative index positions when the zoom positionis displayed on a bar14. the numerical values of representative indices when the zoomposition is displayed on a bar (as many as the number of representativeindex positions)15. normalized placement position information regarding representativeindices on a zoom bar when the zoom position is displayed on the bar (asmany as the number of representative positions)

As described above, the static display information according to thepresent exemplary embodiment includes “the information regarding thedisplay of indices” also for the zoom position. That is, the staticdisplay information according to the present exemplary embodimentincludes a set of information corresponding to the number of indices,pieces of information corresponding to numerical values to be displayedcorresponding to as many indices as the number indicated by theinformation corresponding to the number of indices, and informationcorresponding to the positions where the pieces of informationcorresponding to the numerical values are displayed.

Then, in the present exemplary embodiment, information to be acquired asthe dynamic display information is switched depending on the displaytarget. If the display target is the “zoom position”, the lensmicrocomputer 111 transmits the following information as the dynamicdisplay information to the camera microcomputer 205.

Normalized Placement Position Information on the Zoom Bar when theCurrent Zoom Position is Displayed on the Bar

That is, the lens microcomputer 111 transmits information correspondingto the current position of the zoom lens as the “informationcorresponding to a position” to the camera microcomputer 205. If, on theother hand, the display target is not the “zoom position”, the lensmicrocomputer 111 transmits the static display information described inthe first exemplary embodiment to the camera microcomputer 205.

First, with reference to FIG. 16, a description is given of the displaycontent when the zoom position is displayed on a bar.

A state 1601 illustrates an example where the current zoom position isdisplayed. An icon 1602 indicates the zoom direction on the wide side,and an icon 1603 indicates the zoom direction on the telephoto side. Abar 1604 displays the entire area from the telephoto end to the wide endon a bar. An icon 1605 indicates focal length information as arepresentative index value of the zoom position similarly to the displayof the object distance information. This example of display illustratesthe case of a lens having specs in which the focal length can be zoomedfrom 70 mm to 300 mm. Similarly to the display of the object distanceinformation in the first exemplary embodiment, position informationnormalized with respect to the entire length of the zoom bar from theinterchangeable lens 100 is acquired, thereby determining whichnumerical values are displayed as these representative index values andwhich positions the representative index values are displayed at. Forexample, “70 mm” is displayed at a position of “3” relative to theentire length of the zoom bar, and “135 mm” is displayed at a positionof “50” relative to the entire length of the zoom bar. An icon 1606indicates the current zoom position. The camera microcomputer 205acquires the icon 1606 as normalized zoom position information from thelens microcomputer 111 and displays the icon 1606 at the display unit206.

<Control Flow for Display>

Next, a control flow for display will be described.

The present exemplary embodiment is similar to the first exemplaryembodiment in the flow of the start process described with reference toFIG. 10 and the flow of the steady operation process described withreference to FIG. 11A, except for step S1127 in the communicationprocess of the interchangeable lens 100 and step S1107 in the processingof the camera display unit 206. Thus, the similar portions are notdescribed here. With reference to FIG. 17, a description is given of asubroutine process of the display update process of the camera displayunit in step S1107.

If the subroutine in step S1107 is started, then in step S1701, thecamera display unit 206 determines a timeout status in a case where thedisplay state of the zoom position is set to hidden based on a timer.This mode will be described below in step S1706.

In step S1702, the camera display unit 206 determines whether a targetto be displayed at the display unit 206 is the “zoom position” in thesetting of the menu of the camera. If a display menu is set to the “zoomposition” (Yes in step S1702), then in step S1703, the camera displayunit 206 further determines the setting status of a display menuregarding how to display information. Similar to the first exemplaryembodiment, the display pattern of the zoom position can be set among“always display when MF is performed”, “display for predetermined timewhen focus is adjusted”, “always display”, and “not display”.

If the display setting of the menu is “always display when MF isperformed”, the processing proceeds to step S1704. If the displaysetting of the menu is “display for predetermined time when focus isadjusted”, the processing proceeds to step S1706. If the display settingof the menu is “always display”, the processing proceeds to step S1709.If the display setting of the menu is “not display”, this subroutineends.

In step S1704, the camera microcomputer 205 determines which of the AFstate and the MF state the interchangeable lens 100 notifies the cameramicrocomputer 205 of as the state of the lens focus switch provided inthe lens barrel. As another exemplary embodiment, in a form in which theAF state and the MF state are switched in the camera menu, the cameramicrocomputer 205 may confirm the setting state of the menu. If thestate is the AF state (No in step S1704), this subroutine ends. If thestate is the MF state (Yes in step S1704), then in step S1705, thecamera microcomputer 205 displays the zoom position information.

In step S1706, the camera microcomputer 205 clears the timer for erasingthe zoom position information.

The process of step S1707 is similar to that of step S1705.

In step S1708, to hide the zoom position information in a predeterminedtime, the camera microcomputer 205 sets the timer for erasing the zoomposition information.

If the setting of the menu is assigned to “always display” in stepS1703, the processing proceeds to step S1709. The processing content ofS1709 is similar to that of step S1705.

If the zoom position information display timer times out in step S1701(Yes in step S1701), then in step S1710, the camera microcomputer 205hides the zoom position information.

If the display item is not the “zoom position” in step S1702 (No in stepS1702), then in step S1711, the camera microcomputer 205 proceeds to theprocess for displaying the object distance information described in thefirst exemplary embodiment.

Next, with reference to FIG. 18, a lens communication control unitprocess according to the present exemplary embodiment will be described.As described above, however, the processes of steps S1121 to S1125 aresimilar to those in the first exemplary embodiment.

If the interchangeable lens 100 continues to be attached to the cameramain body 200 in step S1122 (No in step S1122), the processing proceedsto step S1801.

In step S1801, the communication control unit 110 determines whetheroptical information regarding the attached lens 100 changes. If anintermediate accessory is attached between the interchangeable lens 100and the camera main body 200, there is a case where the opticalinformation regarding the lens 100 changes. For example, an extender isbuilt into some model of the interchangeable lens 100. The opticalinformation regarding the interchangeable lens 100, including the focallength, is changed by enabling the built-in extender. For example, FIG.16 illustrates an external appearance 1630 as an example of the productform of the interchangeable lens 100. Various operation members 150 to153 in FIG. 16 are similar to those in the first exemplary embodiment.An operation member 1631 is an operation member for switching theextender built into the interchangeable lens 100. The operation member1631 as a selection switch enables selection of three states, i.e.,“without extender”, “1.4 times extender enabled”, “2.0 times extenderenabled”.

In a case where the optical information changes due to a change in theattached state of the above extender, information acquired for staticdisplay also needs to be updated when the lens 100 is already attachedor when the camera starts in the state where the lens 100 is attached.

Thus, if it is determined in step S1801 that the optical informationchanges (Yes in step S1801), then in step S1802, the communicationcontrol unit 110 acquires the static display information and the dynamicdisplay information as initial values from the interchangeable lens 100and transmits the static display information and the dynamic displayinformation as initial values to the display unit 206 again.

If it is determined in step S1803 that it is necessary to update thedisplay in the camera state (Yes in step S1803), the processing proceedsto step S1804.

In step S1804, the lens communication control unit 110 determineswhether a target to be displayed is the “zoom position” in the menu ofthe camera. If the display target is the “zoom position” (Yes in stepS1804), then in step S1805, the lens communication control unit 110 setsthe dynamic display information to be acquired from the lensmicrocomputer 111 as “normalized placement position information on thezoom bar when the current zoom position is displayed on a bar”, which isrequired to display the “zoom position”. If the display target is notthe “zoom position” but the “object distance information” (No in stepS1804), then in step S1806, the lens communication control unit 110 setsinformation to be acquired from the lens microcomputer 111 to thefollowing information required to display the object distanceinformation described in the first exemplary embodiment.

1. whether object distance information is to be displayed or hidden

2. normalized position information regarding the current object distanceon the distance bar

3. normalized position information regarding the focus limit on theinfinity end side on the distance bar

4. normalized position information regarding the focus limit on theclosest end side on the distance bar

5. normalized position information regarding the macro area on thedistance bar

More specifically, a communication command to acquire the “zoom positioninformation” and a communication command to acquire the “object distanceinformation” are defined and appropriately used according to the cameramenu.

With reference to FIG. 16, a description is given of display contents,for example, in a case where a built-in 1.4 times extender is enabled,and a case where a built-in 2.0 times extender is enabled in step S1801.

A state 1610 illustrates an example where the current zoom position isdisplayed in a case where the 1.4 times extender is enabled. An icon1611 indicates the focal length on the wide side. The focal length atthe wide end is 70 mm when the extender is not present, whereas the icon1611 indicates 98 mm, which is 1.4 times as much as 70 mm, is displayed.

An icon 1612 indicates the focal length on the telephoto side. The focallength on the telephoto side is 300 mm when the extender is not present,whereas the icon 1612 indicates 420 mm, which is 1.4 times as much as300 mm. In this case, a fraction such as 98 mm is displayed on thepremise that the visibility is higher if representative index values aredisplayed at the wide end and the telephoto end of the zoom. However, ina portion where 135 mm is displayed when the extender is not present, ifa fraction such as 189 mm, which is 1.4 as much as 135 mm, is displayed,the display becomes complicated. In response, the interchangeable lens100 generates information as the static display information togetherwith normalized position information to deliberately display a positionof “200 mm”.

By the above communication method between the imaging apparatus and theaccessory device and the above display process in the imaging apparatus,the position where information regarding the zoom position informationto be displayed in the imaging apparatus is displayed is transmitted asa normalized numerical value to the imaging apparatus throughcommunication. Consequently, no matter what imaging apparatus accessorydevices different in specs are attached to, it is possible to performoptimal display.

Further, in the present exemplary embodiment, data regarding scaledisplay for displaying the zoom position information is acquired whenthe accessory device is attached. Then, in a steady state, only theobject distance information regarding the accessory device thatdynamically changes is acquired. In addition to this, based on whether adisplay target is the object distance information or the zoom positioninformation, a communication process is selectively performed, therebyminimizing the communication load. This reduces the influence on varioustypes of control such as AF control, AE control, and image stabilizationcontrol and also enables communication for displaying an object to beperformed frequently, such as every vertical signal timing. Thus, it ispossible to perform various types of driving control and achieve thedisplay of object distance information without delay in the display.Further, also in a case where the optical information changes during anoperation, information required for scale display is acquired again anddisplayed, and when the optical information changes, an index isdisplayed optimally as an optical state after the change. Thus, it ispossible to achieve display facilitating visual confirmation.

According to embodiments of the present disclosure, it is possible toappropriately display information based on an interchangeable lens at acamera display unit.

Other Embodiments

Embodiment(s) of the present disclosure can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present disclosure includes exemplary embodiments, it is to beunderstood that the disclosure is not limited to the disclosed exemplaryembodiments. The scope of the following claims is to be accorded thebroadest interpretation so as to encompass all such modifications andequivalent structures and functions.

What is claimed is:
 1. An imaging apparatus to which an accessory deviceincluding an optical member that changes a shooting condition isattachable, the imaging apparatus comprising at least one processorconfigured to perform operations of following units: a display unitincluding a display area where first index and second index of theshooting condition is displayed; and a communication control unitconfigured to control communication with the accessory device via acommunication unit, wherein the communication control unit receives: (A)information indicating the first index; (B) information indicating aposition of the first index to be displayed relative to the displayarea; and (C) information indicating the second index, wherein the firstindex does not change regardless of change of the shooting conditionwhile the second index changes according to the shooting condition, andwherein both the first index and the second index correspond to sameshooting condition but are displayed at different positions relative tothe display area.
 2. The imaging apparatus according to claim 1, whereinthe shooting condition is distance corresponding to a focus lensposition.
 3. The imaging apparatus according to claim 1, wherein theshooting condition is object distance.
 4. The imaging apparatusaccording to claim 1, wherein the shooting condition is focal distance.5. An accessory device that is attachable to an imaging apparatusincluding a display unit including a display area where distanceinformation corresponding to a zoom lens position is displayed, andincludes a zoom lens that changes the zoom lens position, the accessorydevice comprising: at least one processor configured to performoperations of a communication control unit configured to controlcommunication with the imaging apparatus via a communication unit,wherein the communication control unit transmits: (A) informationindicating a number of indexes of distance information displayed inassociation with the display area; (B) information indicating indexes ofdistance information the number of which is indicated by the number; (C)information indicating a position of each index of distance informationrelative to the display area; and (D) information indicating distanceinformation corresponding to the zoom lens position.
 6. The accessorydevice according to claim 5, wherein in a case where the display unitexecutes display corresponding to first distance information as distanceinformation corresponding to the zoom lens position, and in a case wherethe zoom lens position changes, the communication control unit transmitsinformation indicating second distance information different from thefirst distance information, as (D) the information indicating thedistance information corresponding to the zoom lens position.
 7. Theaccessory device according to claim 6, wherein through communicationexecuted corresponding to supply of power, the communication controlunit transmits (A) the information indicating the number, (B) theinformation indicating as many indexes of distance information as thenumber, and (C) the information indicating the position of each index ofdistance information relative to the display area.
 8. The accessorydevice according to claim 7, wherein even in a case where an operationmember is operated, the communication control unit does not transmit (A)the information indicating the number, (B) the information indicating asmany indexes of distance information as the number, and (C) theinformation indicating the position of each index of distanceinformation relative to the display area again.
 9. The accessory deviceaccording to claim 5, wherein the communication control unit executescommunication in a first communication format or a second communicationformat different from the first communication format, and wherein thecommunication control unit transmits in the first communication format(A) the information indicating the number, (B) the informationindicating as many indexes of distance information as the number, and(C) the information indicating the position of each index of distanceinformation relative to the display area and transmits in the secondcommunication format (D) the information indicating the distanceinformation corresponding to the zoom lens position.
 10. The accessorydevice according to claim 9, wherein the communication control unitexecutes communication via first, second, and third communicationterminals included in the communication unit, transmits data through athird communication channel via the third communication terminalaccording to a change in a signal level in a first communication channelvia the first communication terminal, and receives data through a secondcommunication channel via the second communication terminal according totransmission of the data, wherein in the second communication format,the communication control unit maintains a signal level in the thirdcommunication channel at a predetermined level, thereby notifying theimaging apparatus of a busy state, and wherein in the firstcommunication format, the communication control unit does not notify theimaging apparatus of the busy state.
 11. An imaging apparatus to whichan accessory device including a zoom lens that changes a zoom lensposition is attachable, the imaging apparatus comprising at least oneprocessor configured to perform operations of following units: a displayunit including a display area where distance information correspondingto the zoom lens position is displayed; and a communication control unitconfigured to control communication with the accessory device via acommunication unit, wherein the communication control unit receives: (A)information indicating a number of indexes of distance informationdisplayed in association with the display area; (B) informationindicating indexes of distance information the number of which isindicated by the number; (C) information indicating a position of eachindex of distance information relative to the display area; and (D)information indicating distance information corresponding to the zoomlens position.
 12. The imaging apparatus according to claim 11, whereinin a case where the display unit executes display corresponding to firstdistance information as distance information corresponding to the zoomlens position, and in a case where the zoom lens position changes, thecommunication control unit receives information indicating seconddistance information different from the first distance information, as(D) the information indicating the distance information corresponding tothe zoom lens position.
 13. The imaging apparatus according to claim 12,wherein through communication executed corresponding to supply of power,the communication control unit receives (A) the information indicatingthe number, (B) the information indicating as many indexes of distanceinformation as the number, and (C) the information indicating theposition of each index of distance information relative to the displayarea.
 14. The imaging apparatus according to claim 13, wherein even in acase where an operation member is operated, the communication controlunit does not receive (A) the information indicating the number, (B) theinformation indicating as many indexes of distance information as thenumber, and (C) the information indicating the position of each index ofdistance information relative to the display area again.
 15. The imagingapparatus according to claim 11, wherein the communication control unitexecutes communication in a first communication format or a secondcommunication format different from the first communication format, andwherein the communication control unit receives in the firstcommunication format (A) the information indicating the number, (B) theinformation indicating as many indexes of distance information as thenumber, and (C) the information indicating the position of each index ofdistance information relative to the display area and receives in thesecond communication format (D) the information indicating the distanceinformation corresponding to the zoom lens position.
 16. The imagingapparatus according to claim 15, wherein the communication control unitcontrols communication to execute communication via first, second, andthird communication terminals included in the communication unit,receive data through a third communication channel via the thirdcommunication terminal according to a change in a signal level in afirst communication channel via the first communication terminal, andtransmit data through a second communication channel via the secondcommunication terminal according to reception of the data, wherein inthe second communication format, a signal level in the thirdcommunication channel is maintained at a predetermined level, therebynotifying the imaging apparatus of a busy state, and wherein in thefirst communication format, the imaging apparatus is not notified of thebusy state.
 17. An accessory device that is attachable to an imagingapparatus including a display unit including a display area wheredistance information corresponding to a focus lens position isdisplayed, and includes a focus lens that changes the focus lensposition, the accessory device comprising: at least one processorconfigured to perform operations of a communication control unitconfigured to control communication with the imaging apparatus via acommunication unit, wherein the communication control unit transmits:(A) information indicating indexes of distance information; (B)information indicating a position of each index of distance informationrelative to the display area; and (C) information indicating distanceinformation corresponding to the focus lens position.
 18. An imagingapparatus to which an accessory device including a focus lens thatchanges a focus lens position is attachable, the imaging apparatuscomprising at least one processor configured to perform operations offollowing units: a display unit including a display area where distanceinformation corresponding to the focus lens position is displayed; and acommunication control unit configured to control communication with theaccessory device via a communication unit, wherein the communicationcontrol unit receives: (A) information indicating indexes of distanceinformation; (B) information indicating a position of each index ofdistance information relative to the display area; and (C) informationindicating distance information corresponding to the focus lensposition.
 19. A control method for controlling an imaging apparatus towhich an accessory device including a focus lens that changes a focuslens position is attachable, and which includes a display unit includinga display area where first index and second index of the shootingcondition is displayed, the control method comprising: controllingcommunication with the accessory device via a communication unit,wherein in the control of the communication, the following are received:(A) information indicating the first index; (B) information indicating aposition of the first index to be displayed relative to the displayarea; and (C) information indicating the second index, wherein the firstindex does not change regardless of change of the shooting conditionwhile the second index changes according to the shooting condition, andwherein both the first index and the second index correspond to sameshooting condition but are displayed at different positions relative tothe display area.
 20. A control method for controlling an accessorydevice that is attachable to an imaging apparatus including a displayunit including a display area where distance information correspondingto a focus lens position is displayed, and includes a focus lens thatchanges the focus lens position, the control method comprising:controlling communication with the imaging apparatus via a communicationunit, wherein in the control of the communication, the following aretransmitted: (A) information indicating indexes of distance informationa number of which is indicated by the number; (B) information indicatinga position of each index of distance information relative to the displayarea; and (C) information indicating distance information correspondingto the focus lens position.
 21. A control method for controlling animaging apparatus to which an accessory device including a focus lensthat changes a focus lens position is attachable, and which includes adisplay unit including a display area where distance informationcorresponding to the focus lens position is displayed, the controlmethod comprising: controlling communication with the accessory devicevia a communication unit, wherein in the control of the communication,the following are received: (A) information indicating indexes ofdistance information a number of which is indicated by the number; (B)information indicating a position of each index of distance informationrelative to the display area; and (C) information indicating distanceinformation corresponding to the focus lens position.
 22. A controlmethod for controlling an accessory device that is attachable to animaging apparatus including a display unit including a display areawhere distance information corresponding to a focus lens position isdisplayed, and includes a focus lens that changes the focus lensposition, the control method comprising: controlling communication withthe imaging apparatus via a communication unit, wherein in the controlof the communication, the following are transmitted: (A) informationindicating indexes of distance information; (B) information indicating aposition of each index of distance information relative to the displayarea; and (C) information indicating distance information correspondingto the focus lens position.
 23. A control method for controlling animaging apparatus to which an accessory device including a focus lensthat changes a focus lens position is attachable, and which includes adisplay unit including a display area where distance informationcorresponding to the focus lens position is displayed, the controlmethod comprising: controlling communication with the accessory devicevia a communication unit, wherein in the control of the communication,the following are received: (A) information indicating indexes ofdistance information; (B) information indicating a position of eachindex of distance information relative to the display area; and (C)information indicating distance information corresponding to the focuslens position.